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Motorized units and slope

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The manual states that "motorised units can only traverse ground with more than a 30 degree slope if a road is present." That means that Motorized should be able to traverse any ground with less than or equal to a 30 degree slope without a road being present.

I am playing the "Island Prize" scenario and one of the German units is the 14th Motorized Anti-Tank Company, which is motorized and comes in as a reinforcement along the coast. However, the unit can only move a slight distance from it's arrival location. What seems to be keeping the unit from moving very far is when the ground slope is 21 degrees. (see screenshot below)

Is this a bug in the scenario? In the code? An error in the manual?

I find it hard to believe I am the first person to notice this issue in this scenario, but I can't find any other discussion about it.
 

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GoodGuy

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Can you provide a screenshot of the E&S tab of the unit?
I'd like to see what tow vehicles are present and what AT guns are used (PaK 36 most likely). The Pak 36 was relatively small and could be pulled with a Kübelwagen (quite some Army officials and officers didn't like the troops to do that, as it increased car breakdowns and the need for maintenance, and as the higher speeds tended to ruin the gun carriages), but the gun was supposed to be pulled with dedicated tow vehicles or trucks.
A regular truck would have had a hard time on that slope/terrain and an even harder time if it had to pull a somewhat finicky Pak 36 carriage.
In the other thread, where you posted the google screenshot of the location, I forgot to mention that the engine actually does compute the slope/terrain layout between separate height layers, so it's not like the beach line is completely flat.
The wording in the manual ... 30 degrees from horizontal (0 degrees), right?

slope.jpg


The actual edge of the coastline (right at the water) should have a pretty low slope (the slope might even be as low as say 1-5 degrees). Check it out and move the move order marker closer to the water.
The engine has a function that readjusts the movement order marker to the nearest accessible location. As a general example, the main slope will be averaged across a certain width between those 2 layers, the marked width is a generic example and marks the main slope. The slope then decreases right of the right-hand bracket. Try a spot just near the water. Or, alternatively, try a point 1 or 2 kilometers south of that move order position, to see what the pathfinding concludes. If it concludes that the "beach" isn't accessible, then the map design is actually more accurate than I assumed (in the other thread), means the supposed accessibility is just caused by the (wrong) visual impression where the viewer is tempted to see it as flat beach area, but where the engine comes up with a proper/realistic result (a calculated slope in the main transition area between the 2 height layers). Usually, the maps in CO (and its predessors) are quite sophisticated/realistic, just some details turn out differently, at times (eg. the missing plateau).

EDIT: I actually misinterpreted the rather flat looking beach layer, too (it's been a while since I last played CO), as I can't click on those map parts (game not installed).

I think the designer used both - historical map material and modern maps/terrain layouts - but the focus may be put on historical maps with some game maps, sometimes, so that some details (eg. the plateau) do not show up.
 
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GoodGuy

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Now, the 21 degrees:

prozent.png

21 degrees would have been a challenge for many WW2 vehicles, but some 4x4 vehicles, empty Kübelwagen etc. and tracked vehicles may have been able to climb such section, if the ground was halfway solid, in theory.

But a slope of 21 degrees, combined with the rough terrain in RL, is even worse than the slope on this street (Baldwin street, NZ, 19.3 degrees):

https://en.wikipedia.org/wiki/Baldwin_Street#/media/File:Baldwinstreet.jpg

EDIT: I cannot imagine how (and which) vehicles would be able to climb a slope of 30 degrees for more than a few meters, to be honest.

Climbing a slope of 21 degrees may have appeared to be an impossible mission for a weak Kübelwagen already, if it had to pull an AT gun that weighed ~ 700 kg, for instance. A motorcycle would have been able to climb it, and an empty 4x4 truck may have been able to climb some or even most sections, too, I guess.

EDIT: Interestingly, Churchill tanks were able to climb such slopes. After the Battle of Longstop Hill, Churchill I Mk IV tanks of the North Irish Horse Regiment managed to climb a slope - that was described by British participants (according to Bryan Perret in "At All Costs: Stories of Impossible Victories." 1998) as slope that featured 1:3 gradients in some places (33,3% = 18.42 degrees, if I am not mistaken) - that led up to Djebel Rhar, which was held by the Germans.
Prior to the daring tank assault, the Germans had plastered and denied a British diversionary infantry attack on the southern flanks of the hill with accurate/heavy mortar fire, but they had not put up tank obstacles or AT guns at the hill section covering the north-western slope, as they assumed that the heavy Churchills could not climb such slope/terrain. The first Churchill (of the tank group that had climbed the NW approach) reached the peak and literally breached the German HQ perimeter, and captured 50 surprised Germans in the process.

EDIT: Australian trials in the muddy terrain of New Guinea, using Churchill Mk IV, V and VII, and M4A1 and A2 tanks (video below):
Side slopes were vital parts in these tests. At around 6:31 in the video you can hear that a side slope (tilt) of 22 degrees "presented no difficulty" for a Churchill moving on the soft (if not muddy) grassland.
The Shermans were able to climb hills that featured slopes with "max. angles of 34 degrees" near the hilltops (~ 6:52 in the video). The Shermans then had difficulties to descend those slopes, due to the muddy terrain (and the rather low weight of the tanks, which made them slide down, often). The Churchill descended like on rails, due to the high weight.

The Churchills had no problems climbing the soft 34-degrees slope either, they climbed it easily actually.
Now imagine these tanks moving on the rather solid ground on Leros or in Tunisia
After watching the trial footage, I tend to think that both tanks could even climb somewhat steeper gradients (above 34°):


Interesting detail at 19:48 : The Churchills had to be covered with canvas covers during tropical downpours (during monsoon or the typical and frequent Asian pacific heavy rains coming out of nowhere), because the "gutters and water takeoffs incorporated in the tank design were never intended for so much water in such a short time."

M24 Chaffee and Matilda trials:
The Chaffee manages to climb the final bit of a slope with a 30-degrees gradient in one scene, the voice-over stresses that the tank barely made it, though. 20-degrees slopes could be climbed easily (even in 2nd gear). The tank failed to climb grassy slopes (30 degrees), due to the lack of traction and ground pressure. The sections starts at ~ 11:05 :


--

British trials examining hill climbing capabilities of the Churchill tanks:
http://discovery.nationalarchives.gov.uk/details/r/C6144347
(Hill climbing, gravel and grass, Churchill tests, standard suspension and alternate bogies removed (F.V.P.E. Report No. FT.1332/1)(1944)

Other tracked vehicles could also climb such slopes.

I am not sure to what extent the engine considers the angle of approach, though, as there would be no incline if the slope would be approached from the north (green arrow, pic below), the vehicle would just be tilted (21 degrees on its X-axis, means its longitudinal axis, so that it could go straight on a side slope). As long as the tyres or tracks keep the grip and gravity doesn't kick in, vehicles should be able to cross such section, if they use a 90-degrees approach:

slope-approach.jpg

I hope that made sense. So, I think you are right, some of these areas should be accessible with that map design for certain vehicles, if the vehicles use a near-vertical approach. In order to have a more realistic depiction of the real area that is packed with stones, sand and other obstacles, most parts of the shoreline should be converted using the "rough terrain" overlay, to deny wheeled vehicle movement on a number of sections that are further away than say a strip of 5-10 meters right at the water, imho.
That would also create a realistic bottleneck that would cater for the fact that the immediate coastline is kind of accessible to most if not all vehicles, except for the sections with flumes.

I can't remember if rough (impassable) terrain can be accessed by tanks or not.
Imho, there should be terrain that can be passed by tanks but not by wheeled vehicle types (if it isn't in the game already), as quite a few tanks could handle the slopes in the Leros area .
 
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GoodGuy

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One more video :):
This biased video (you will notice the red X's for an early underpowered Sherman failing trial tasks) uses footage from the Swedish trials, where the performances of several Sherman versions (VVSS vs. HVSS suspension with wider tracks, etc.) were compared to the cross-country performance of the Panther. In the Australian trials, even the Shermans with narrow tracks got sufficient grip on soft ground, due to the coconut fiber, grass and roots creating additional traction on some of the New Guinea trial grounds.

The Swedish terrain didn't offer such benefits, so the early Sherman performed worse.

So the early Sherman was disadvantaged (as the early Sherman had narrow tracks and as some Sherman versions were underpowered in regards to the total weight - eg the Sherman Firefly) during the Swedish trials, but the trials also showed that the Panther could climb a gradient of up to 40 degrees (~35 degrees acc. to no. of reliable books). I am not sure if the 40 degrees were officially established by the Swedish military. IIRC, the Panther broke down later on (gearbox ruined):


And one more pic :):

churchill-climbing.jpg

I do understand that a game designer has to finalize a max value at one point, but 30 degrees would definitely not be the correct max. value for a number of WWII tanks.
 
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The manual states that "motorised units can only traverse ground with more than a 30 degree slope if a road is present." That means that Motorized should be able to traverse any ground with less than or equal to a 30 degree slope without a road being present.

I am playing the "Island Prize" scenario and one of the German units is the 14th Motorized Anti-Tank Company, which is motorized and comes in as a reinforcement along the coast. However, the unit can only move a slight distance from it's arrival location. What seems to be keeping the unit from moving very far is when the ground slope is 21 degrees. (see screenshot below)

Is this a bug in the scenario? In the code? An error in the manual?

I find it hard to believe I am the first person to notice this issue in this scenario, but I can't find any other discussion about it.


There is a "performance" attribute for vehicles which includes a "Maximum Gradient" parameter.

That parameter defines the maximum slope the vehicle can traverse perpendicularly to the gradient lines (defined in the game as altitude layers on the map used to calculate a slope over a distance).

I'm not certain how the calculation is performed, but if it is like unit speed calculations, it would use the capability of the primary form of motorized transport for the unit first considering whether the primary transport is tracked or wheeled and then considering what Maximum Gradient parameter that majority share for performing the calculation.

Maximum Gradient is defined on Pg. 22 of the Estab Editor manual.
 

GoodGuy

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But vehicles with medium and heavy weights should then still be able to cross/access a side slope of say 21 degrees (as in Titanium's example/screenshot). The videos clearly demonstrate that such side slopes posed no problems to medium and heavy tanks, and a 4x4 truck or tow vehicle (wheeled or tracked, and bigger/more powerful than a Kübelwagen) wouldn't have had a problem on the solid ground (in conditions depicted on this Leros map) either.
I start to think that the engine only considers the marker's position and then performs a calculation of a perpendicular approach (on the gradient), which would not be needed for the actual movement direction of the unit/vehicles - they go straight on a side slope.
In fact, the unit would even move downhill on the first third of the ordered move, if you look at Titanium's screenshot.

It would be nice if Dave (or one of the mappers) could provide some info here.
 
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But vehicles with medium and heavy weights should then still be able to cross/access a side slope of say 21 degrees (as in Titanium's example/screenshot). The videos clearly demonstrate that such side slopes posed no problems to medium and heavy tanks, and a 4x4 truck or tow vehicle (wheeled or tracked, and bigger/more powerful than a Kübelwagen) wouldn't have had a problem on the solid ground (in conditions depicted on this Leros map) either.
I start to think that the engine only considers the marker's position and then performs a calculation of a perpendicular approach (on the gradient), which would not be needed for the actual movement direction of the unit/vehicles - they go straight on a side slope.
In fact, the unit would even move downhill on the first third of the ordered move, if you look at Titanium's screenshot.

It would be nice if Dave (or one of the mappers) could provide some info here.
Vehicles with the appropriate attributes defined in he Estab can perform the task. Has nothing to do with weights of individual vehicles,unless the the Estab developer takes those into account when codifying the attributes for the vehicle.

As I said, the controlling attribute is the Maximum Gradient parameter assigned by the Estab creator and used in calculations of mobility as defined in the Estab Editor manual. How that the entire game mobility gets calculated is part of the game's proprietary software. How that affects a unit's movement capability is a best guess based on an analogy to discussion with the developers of how a unit's combat speed is determined in the proprietary software.

There are no "mapers" except volunteers who develop scenarios for commercial release. I did one rather complicated map for a user developed scenario that included significant contour variations as part of the combat terrain. I likewise created an Estab for US Marine Corps and Imperial Japanese Army and Navy combat units which included as realistic portrayal of vehicle attributes for new amphibious transport for the Marines and Japanese light arms, armor and artillery pieces that were not available in any Estab.

I learned a lot about Mapmaking and Estab editing, particularly as I transitioned that scenario from a CO1 standard to teh CO2 standard.

All worked as expected within the proprietary game software.

Dave can offer insight to the proprietary software, but I have worked with the Map Making, Estab Editing, and Scenario Making software to discover what I think is some useful information to offer to players who ask questions here.

Your historical anecdotes are interesting and important data for a proficient mapmaking, estab editing and scenario making developer to considier when codifying platform behaviors. But they shed no light on why the game performs as it does, or how to work with the game engine to attain the combat results a player could use for success in playing the game..
 

GoodGuy

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Vehicles with the appropriate attributes defined in he Estab can perform the task. Has nothing to do with weights of individual vehicles,unless the the Estab developer takes those into account when codifying the attributes for the vehicle.

I mentioned the weight solely in reference to RL physics.

As I said, the controlling attribute is the Maximum Gradient parameter assigned by the Estab creator and used in calculations of mobility as defined in the Estab Editor manual. How that the entire game mobility gets calculated is part of the game's proprietary software. How that affects a unit's movement capability is a best guess based on an analogy to discussion with the developers of how a unit's combat speed is determined in the proprietary software.

I referred to the range of software/engine calculations applied to movement orders and pathfinding when unit X approaches slope Z from a non-perpendicular direction (means no frontal approach on the slope, where the frontal appr. would be a movement up- or downhill).

There are no "mapers" except volunteers who develop scenarios for commercial release. I did one rather complicated map for a user developed scenario that included significant contour variations as part of the combat terrain. I likewise created an Estab for US Marine Corps and Imperial Japanese Army and Navy combat units which included as realistic portrayal of vehicle attributes for new amphibious transport for the Marines and Japanese light arms, armor and artillery pieces that were not available in any Estab.

I am well aware that mappers were/are volunteers, recruited beta testers etc. I started to frequent the Matrix HTTR forum in 2006, and I had lurked in 2005 already. I also published a semi-fictional map/user scenario depicting a German Rhine valley for HTTR the same year. Since there was no Estab editor available at the time, I had to resort to taking away weapons and vehicles, in order to simulate Volkssturm units. Downside: When the resupplies kicked in 1 time per day (at 3 a.m.), such units drowned in heaps of ammunition, it was not possible to simulate low supplies. I also worked on Greek island user scenarios for COTA, but I stopped working on it when a similar scenario (was it Leros?) and one or another similar map appeared. And I playtested PoE's North African user scenarios.

Your historical anecdotes are interesting and important data for a proficient mapmaking, estab editing and scenario making developer to considier when codifying platform behaviors. But they shed no light on why the game performs as it does, or how to work with the game engine to attain the combat results a player could use for success in playing the game..

My posts had 2 aims: a) assessing/presenting the historical capabilities and b) trying to find out how the game's algorythms handle a straight approach on a side slope, and if the calculations lead to situations where the engine would then deny units access to certain areas, where a particular map layout would allow units to get to these areas in a similar real life environment.
Dave could explain how the game code handles such instances.

I also used the term "mappers" as general term for those guys with more detailed knowldege, ie. some of the guys who created a number of original HTTR + COTA maps, and/or who were part of the early "beta bunnies". MarkShot, for instance, was one of these guys, he had additional knowledge about engine calculations and about how the code would handle certain units or orders, and he could often jump in when Dave was too busy. Very specific coding questions could only be answered by Dave or Paul, ofc.
 
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After reading through the manuals and learning how to use the Estab and Scenario editors, I have come to the conclusion that the manual is wrong. Each individual vehicle has it's own "Max Gradient" parameter (as jimcarravallah pointed out above) and it seems to vary between around 20° and 60°(!). The 4th Motorized Anti-Tank Company mentioned in the original post has 8 German 1.5 t trucks attached to it and they have a a Max Gradient of 20°, so that is why that unit can't traverse slopes equal to 21° or greater.

The Island Prize scenario should be edited to remove the two Motorized Anti-Tank Companies as they are useless where they arrive (due to not being able to move more than a few hundred meters because of the large slopes on the island) and there is no way to edit the vehicles out of the unit in the scenario editor. The idea that the Germans were landing 1.5 t trucks on the rocky coast of the island of Leros during the battle is far fetched anyway.

Below is a picture of some vehicle information from the game. As you can see, the Jeep and the Sherman can somehow manage a 60° degree slope, which is the equivalent of going up 1 ft for every 0.6 ft you go forward. GoodGuy's post above does an excellent job of showing what reasonable slopes could be achieved by WWII vehicles, and 60° seems not just unlikely, but impossible at the scale the map is modeled.

Perhaps some research should be done on what's actually in the Estabs and what was reasonable for WWII equipment.

Max Slopes.png
 
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GoodGuy

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After reading through the manuals and learning how to use the Estab and Scenario editors, I have come to the conclusion that the manual is wrong. Each individual vehicle has it's own "Max Gradient" parameter (as jimcarravallah pointed out above) and it seems to vary between around 20° and 60°(!). The 4th Motorized Anti-Tank Company mentioned in the original post has 8 German 1.5 t trucks attached to it and they have a a Max Gradient of 20°, so that is why that unit can't traverse slopes equal to 21° or greater.

The Island Prize scenario should be edited to remove the two Motorized Anti-Tank Companies as they are useless where they arrive (due to not being able to move more than a few hundred meters because of the large slopes on the island) and there is no way to edit the vehicles out of the unit in the scenario editor. The idea that the Germans were landing 1.5 t trucks on the rocky coast of the island of Leros during the battle is far fetched anyway.

Below is a picture of some vehicle information from the game. As you can see, the Jeep and the Sherman can somehow manage a 60° degree slope, which is the equivalent of going up 1 ft for every 0.6 ft you go forward. GoodGuy's post above does an excellent job of showing what reasonable slopes could be achieved by WWII vehicles, and 60° seems not just unlikely, but impossible at the scale the map is modeled.

Perhaps some research should be done on what's actually in the Estabs and what was reasonable for WWII equipment.

View attachment 8391

Does the estab or the E&S tab provide any info about what sort of tow vehicles are used to pull the AT guns? Which AT guns are used?

If the 1.5-ton truck "3-t truck Ger" (which would be a non 4x4 Opel "Blitz" for instance) on the screenshot is used as tow vehicle in that unit, then the estab entry would be wrong, as the Krupp "Protze" (Krupp L 2 H 43 with 55 HP, issued from 1933–1936, or the L 2 H 143 with 60 HP, issued from 1937–1941) used to be the dedicated tow vehicle for the PaK 36, but was also used to tow the light Flak guns (eg. Flak 30, Flak 38, and the quad-Flak "2-cm-Flak-Vierling 38", all of these were 20-mm Flak guns) at the time.

https://de.wikipedia.org/wiki/Krupp-Protze#/media/Datei:Kfz70.jpg
http://www.fahrzeuge-der-wehrmacht.de/Artikel/Krupp_L2H43.html

The vehicle had 6 wheels, a beam axle in the front and rear-wheel drive (both rear axles were powered as 2 limited slip differentials were used), so the Krupp vehicle had way better grip than a non-4x4 truck (eg. the early 1.5 version of the Opel Blitz; only the 1940 "A"-version of the 3.6-ton version of the Blitz S = "Standard", which was produced from 1940 - 1949, was a 4x4 vehicle; A = "Allrad") and was an all-terrain vehicle in general, but it might not have been as capable as a real 4x4 truck (with powered front axle) because the front axle was unpowered. Still, I can't imagine that a Krupp L2 tow truck would have had a hard time to cross the side slope section in your original screenshot.
The Protze was also used as signal car (radio/telephone), staff field HQ car, as mobile radio tower, as dedic. tow vehicle for the Flak 30 and 38 and troop transport vehicle for somewhat rougher terrain. Max. speed: ~ 70 km/h.
Its engine was also used in the Panzer I and in the armored scout car SdKfz 247 A.

I do remember that 99% of the COTA estabs were amazingly accurate, though, the presence of the Protze and other vehicles/details was taken into account for all relevant units, usually. The engine just dosn't seem to be able to fully simulate the high speeds of the German 6- and 8-wheeled scout cars (80 km/h and 90 km/h, the Brits had scout cars with similar speeds, like 70-80 km/h ), as the slower vehicles in such coys seem(ed) to lower such units' avg. speeds (at first glance at least, I am not sure if it's still like that), that's why I suggested to outsource such vehicles and put them in separate platoons so that they can move around with full speed, a few yrs ago.

A number of motorized Artillery regiments employed hybrid vehicles as fast observation/scout vehicles in their recon elements, namely the SdKfz 254 (medium observation scout car/halftrack, also known as Saurer RR-7, 12 pre-production models and ~129 vehicles were built), which could move fully tracked but also lower 4 wheels to move faster on roads to reach observation points and evacuate more quickly.
On paper, and looking at the number 254, the vehicle could be confused with regular halftracks. You can see 2 pictures here:

http://www.kfzderwehrmacht.de/Haupt...erreich/Saurer/Sd__Kfz__254/sd__kfz__254.html

Whatsoever, I don't see why a Protze and similar tow vehicles shouldn't have been able to pass a side slope on a straight approach (the gradient level below is just a random example), if it wasn't overloaded (most of the stuff in the truck below would have been unloaded or moved to the car's right side, most likely :p) :

side-slope-protze.jpg

So the question remains, imho: how does the engine handle such approaches?
 
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GoodGuy

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Thanks for the info.

The authorized standard tow vehicle for the Pak 38:

le. Zugkraftwagen 1t (SdKfz 10, a light halftrack, not a truck)
I wouldn't rule out that other halftracks were added to the list later on, but this was the assigned prime vehicle.

https://de.wikipedia.org/wiki/Sd.Kf...406-19,_Russland,_Zugkraftwagen_im_Winter.jpg

Such halftrack could easily access the slope in your screenshot, even uphill (and with the gun attached).

Improvised solutions (where most of them were included/authorized in KStN sheets, though) to make up for the general lack of halftracks, trucks and tow vehicles in the Wehrmacht:

- Mercedes-Benz L 1500 S/A (WA 170), this was a non-4x4 vehicle with rear-drive
https://de.wikipedia.org/wiki/Merce..._Russland,_Offiziere_in_Mercedes-Benz_Kfz.jpg

- Gepanzerter Artillerieschlepper 630 (r) (WA 170), this was the captured Russian "Komintern" tracked tow vehicle which was used to tow the Russian divisional arty pieces (107 mm - 152 mm guns) in the Soviet Army, and which was then captured and incorporated in the German Army during Barbarossa and then mainly used on the EF to tow a range of guns in winter/during mud season.
https://upload.wikimedia.org/wikipedia/commons/a/a7/Komintern_artillery_tractor.jpg

- Gepanzerter Infanterieschlepper UE 630 (f) (WA 170), a captured French Renault armored tow vehicle, mainly used by the Germans to tow guns and ammunition trailers (Munitionsschlepper UE 630 f), variants were conversions to rocket launchers, radio vehicles, MG carriers, explosives carriers, telephone line layers, observation vehicles, pushback vehicles on airfields and frontline airstrips, or to snowplow vehicles for the EF.
EDIT: The trailer had light armor and the trailer bed could be tilted from inside the tow vehicle so that ammo crates could be delivered/dumped even under sporadic/light enemy fire. This mechanism/method allowed the Germans to savely dump ammo into friendly frontline trenches, for instance. They were also used to perform emergency supply runs for armored units in contested areas. In general, the dedicated tow versions were used to pull a range of PaKs (37-mm to 76,2-mm AT guns) and light inf guns.
https://de.wikipedia.org/wiki/Renault_UE_Chenillette#/media/Datei:Renault-UE-Saumur.00048b3a.jpg

- Gepanzerter Vollkettenschlepper VA 601 „KNIL“ (WA S-42), a captured Belgian "Vickers utility tractor" (armored)
http://www.kfzderwehrmacht.de/Haupt...lity_Tractor_Typ_B/utility_tractor_typ_b.html

- Laffly-Licore V15 R (WA 170), a captured French 4x4 tow vehicle that was designed to pull the French light AT guns, eg. the Hotchkiss 25-mm SA.
http://www.kfzderwehrmacht.de/Homep...rance/Laffly/Laffly_S_15_R/laffly_s_15_r.html

The Germans also used other (bigger) halftracks (rather irregular use, as they were supposed to tow bigger arty pieces), but rarely regular trucks (but they used the Blitz, when its 3.6-ton 4x4 "A" variant came up in 1940, occasionally; such use was still unauthorized, afaik, though), and only when halftracks weren't available, basically, as the Pak weighed ~ 985 kg in travel mode.
 
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simovitch

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I though we addressed this back in the matrix days, but I believe that when the manual says degrees what it really means is "percent". so a 45d slope would be 100%. One of the coders would have to chime in to put this to sleep.
 

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Now that you mention it, that sounds somewhat familiar ...
But a 21% gradient would be a slope with 11.86 degrees only.


717px-Slope_quadrant.svg.jpg


22prozent-2.jpg

Besides, it still wouldn't explain why a vehicle wouldn't be able to cross a side slope of 21%, where it then wouldn't have to climb any slope, as the gradient would amount to 0 %/degrees.
 

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EDIT: Interestingly, Churchill tanks were able to climb such slopes. After the Battle of Longstop Hill, Churchill I Mk IV tanks of the North Irish Horse Regiment managed to climb a slope - that was described by British participants (according to Bryan Perret in "At All Costs: Stories of Impossible Victories." 1998) as slope that featured 1:3 gradients in some places (33,3% = 18.42 degrees, if I am not mistaken) - that led up to Djebel Rhar, which was held by the Germans.
Prior to the daring tank assault, the Germans had plastered and denied a British diversionary infantry attack on the southern flanks of the hill with accurate/heavy mortar fire, but they had not put up tank obstacles or AT guns at the hill section covering the north-western slope, as they assumed that the heavy Churchills could not climb such slope/terrain. The first Churchill (of the tank group that had climbed the NW approach) reached the peak and literally breached the German HQ perimeter, and captured 50 surprised Germans in the process.

EDIT: Australian trials in the muddy terrain of New Guinea, using Churchill Mk IV, V and VII, and M4A1 and A2 tanks (video below):
Side slopes were vital parts in these tests. At around 6:31 in the video you can hear that a side slope (tilt) of 22 degrees "presented no difficulty" for a Churchill moving on the soft (if not muddy) grassland.
The Shermans were able to climb hills that featured slopes with "max. angles of 34 degrees" near the hilltops (~ 6:52 in the video). The Shermans then had difficulties to descend those slopes, due to the muddy terrain (and the rather low weight of the tanks, which made them slide down, often). The Churchill descended like on rails, due to the high weight.

The Churchills had no problems climbing the soft 34-degrees slope either, they climbed it easily actually.
Now imagine these tanks moving on the rather solid ground on Leros or in Tunisia
After watching the trial footage, I tend to think that both tanks could even climb somewhat steeper gradients (above 34°):


Interesting detail at 19:48 : The Churchills had to be covered with canvas covers during tropical downpours (during monsoon or the typical and frequent Asian pacific heavy rains coming out of nowhere), because the "gutters and water takeoffs incorporated in the tank design were never intended for so much water in such a short time."

M24 Chaffee and Matilda trials:
The Chaffee manages to climb the final bit of a slope with a 30-degrees gradient in one scene, the voice-over stresses that the tank barely made it, though. 20-degrees slopes could be climbed easily (even in 2nd gear). The tank failed to climb grassy slopes (30 degrees), due to the lack of traction and ground pressure. The sections starts at ~ 11:05 :


--

British trials examining hill climbing capabilities of the Churchill tanks:
http://discovery.nationalarchives.gov.uk/details/r/C6144347
(Hill climbing, gravel and grass, Churchill tests, standard suspension and alternate bogies removed (F.V.P.E. Report No. FT.1332/1)(1944)
Funny thing that people glorify Renault FT that was a horrible dead-end concept that spawned only the horrible French tanks with one man turret and horrible ergonomics while the successor of Mark V was one of the finest tanks of WWII.
 

GoodGuy

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The FT was a terrible tank, as it offered protection against rifle/MG projectiles in theory/on paper, but the pure impact of such projectiles would often create splinters/spallings inside, which could create terrible face injuries. Crews of the Mark V used to wear special face masks for protection, as the front section of the Mark V had 16-mm armor plates (8 - 20-mm in the FT) only, so they had to deal with similar spallings.

But the FT introduced features that carried over to today's tank designs:
- gun system embedded in a fully rotatable turret,
- engine in the rear (behind the crew, whereas the engine in the Mark V resided in the center of the crew compartment),
- telescopic sight for the gunner,
- compact size leading to the development of light and medium tanks in the 1930s and to the first medium tank doctrines that envisioned medium tanks to be dedicated infantry-support vehicles and even main battle tanks that could fight enemy tanks.

Unlike its predecessors, the Mark V's had no air flow inside the crew compartment, because the roof fan's performance was too low. The crew was usually unfit for service after a few hrs of combat, due to engine emissions and gun smoke inside the crew compartment.
The noise level made crew comms very difficult.
The Independent Heavy Tank from Vickers (1 prototype, a multi-turreted tank) was more influential, not because its design influenced the Russian multi-turret designs (a spy handed over detailed plans to the Soviets), which were dead-end developments, but because it allowed the tank commander to use an intercom to communicate with his crew (7 men), a feature used in all modern tanks in WWII (then with earphones and throat-mikes) and even today.

That said, the Mark V was clearly the dead end, not the FT, imho. :)
The stretched Mark V, used for troop transports, is seen as the first APC in history, though, an asset employed in all modern armies.

The French just drew the wrong conclusions and "disimproved" the design by introducing well armored but severely underpowered tank designs, instead of taking the superior rotatable-turret design to the next level (like those nations that created fast/agile tank platforms).

On top of that, bad tactical deployments, the lack of short range radios for communication on the platoon level and the atrociously low speed then limited their effectiveness in 1940.

EDIT: While the 1-man setup in the FT was the result of the small dimensions, keeping this concept for the designs of France's 1930s light and even medium (in the S35 + the D2) and heavy tanks (B1) was just a crazy idea, I'd agree there. They could have at least upped the dimensions/ergonomics to offer sufficient space for an additional loader.
It seems like the developers and the French army still clinged to outdated WWI tactics/requirements, to some extent at least.

The Russians faced similar ergonomic/view problems with their cramped 2-man turrets in the early T-34 tanks, though, only the introduction of resized turrets with 3-man setups could correct these problems. But the tank was still an effective platform and its dimensions/performance facilitated the introduction of upgrades.
 
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Perturabo

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Both Mark tanks and A7Vs had telescopic sights.

The "revolutionary" features of Renault FT aren't exactly so revolutionary. Warships and armoured cars already had turrets. Main problem is in the conception behind the tank, which isn't of modern tank, while conception behind Mark V is.

The conception of Renault FT is to create an armoured infantryman. This is the same conception as behind later tankettes. In a way, Renault FT is the first tankette.
It brings its significant limitations which are inherent in the concept - that is the crampiness and gunner being commander. It's a result of the idea of armouring an infantryman which resulted in minimum crew necessary to operate the vehicle, not optimum crew for functioning of it. It's because the whole idea behind the tank was wrong and worked only because of deployment in swarms and enemy not having much tanks and AT guns.

To quote Tanks in the Great War:
"Meanwhile, General Estienne in June visited England, and having seen the British Mark I machine was convinced of the necessity of a lighter tank. This tank was the result of an idea he had in mind, namely, of producing on the battlefield waves of skirmishers in open order; each skirmisher to be clad in armour, and to be armed with a machine gun which could be used with uninterrupted vision in all directions. The weight of armour necessitated an auxiliary means of motion; this, in its turn, gave rise to the necessity for another man to drive the machine. These views General Estienne laid before the Renault firm in July 1916, and at the same time he urged the Ministry to accept his proposed light tank, but without success."

General Estienne started out well with assault guns but then he started having seriously bad ideas that ruined the French tank development for decades. They continued to build tanks based on this concept and worse turret designs stayed true to it even for heavier "tanks" like Char B and Souma S-35. Even their concept of cavalry tank in practice was more like an armoured knight than a proper AFV. It's a concept that infected French tank development and ruined it.

Modern tanks are directly descended from the British concept of Landship - note that both battery ships and monitors are still variants of a an ironclad warship. The concept of putting turret on AFV existed long before Renault FT. Originally Mark tanks were supposed to have turrets, but they weren't implemented because of concerns about centre of gravity and stability of the vehicle.
Turret and engine location are technical details.
The most important feature of modern tanks is crew specialisation, including the institution of tank commander (ship's captain) and also crew communication and observation.
I consider Mark V to be the first modern tank because it had a dedicated commander observing the battlefield from his commander's booth, it had crew communication in form of voice tubes and target indicators for gunners.
I suspect that despite a lack of turret, a modern tank commander would feel more at home in Mark V than in Renault FT. At least he could be a tank commander instead of an armoured infantryman.

M1 Abrams can be considered a land warship. It isn't an armoured infantryman though - it's not small, it doesn't have minimal crew, it doesn't have a gunner-commander.

French had actual modern tanks, with large guns and three man turrets - FCM 1A. They never entered mass production - possibly due to Estienne's meddling and even after producing FCM 2C, they stopped designing 3 man turrets due to following the stupid concept behind Renault FT. Of course, these FCM tanks were developed by shipyard.

Generally, I see tank history basing on services that developed them and ideas behind them, more than specific design details.

Funny thing is that while oversized Mark Vs turned out to be unusable as APCs, A7V was an actual practical IFV. They made far bigger impact than their numbers would suggest. During initial battles of the Spring Offensive, they'd carry dismounts and also crews would partially dismount and fight in absence of infantry. Female version also carried two flamethrowers for dismounts.
The initial A7V detachments had stormtrooper training.

At St Quentin:

"At that moment the expected support has arrived. Two German tanks, mobile fortresses, similar to British vehicles but larger, drove noisily from passage from Grugis and attacked Entente position from the flank.

In short time whole vicinity was cleared of obstacles. We could move forwards. Crews of two tanks fired at enemy from side with gun and machine guns. We folded defence of a few trenches. In a few incidents teams of tank crews exited the their machines and attacked the enemy with hand grenades and flamethrowers".

In Villers-Bretonneaux, during urban combat they suppressed defenders with machine guns and dismounts cleared them out.

"I jump out of the tank with several of my men. We attack the enemy with hand grenades. It caused that we turned 30 soldiers into 6 prisoners. [...] But it's nothing exceptional for me, because we're all infantrymen."

Unsurprisingly A7V was work of a transport department.

So, we have British navy with Landships, Estienne, the artilleryman with assault guns and German transport department with IFVs.

Land warship was a very successful concept, assault guns were very successful concepts, IFVs are still around here, though they didn't catch on until cold war. Tankettes... were quite meh. They were basically something that was better than no tank, but that's it.

I'd say Panzer I and II pretty much pushed the concept behind FT to the limits - used in swarms and coordinated through radios. And the limits were reached quite fast, leaving large tanks with specialised crews.
 

GoodGuy

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In Villers-Bretonneaux, during urban combat they suppressed defenders with machine guns and dismounts cleared them out

"I jump out of the tank with several of my men. We attack the enemy with hand grenades. It caused that we turned 30 soldiers into 6 prisoners. [...] But it's nothing exceptional for me, because we're all infantrymen."

Parts of the crew left the tank, but they had to abandon their assigned positions/guns in the tank to do that. There was no room to carry infantry sections and the crew consisted of a number of specialists: artillery gunners, MG gunners, loaders, driver, machinist(s), commander. All had infantry training ofc, but the tank was not designed to ferry "tankborne" inf troops, and each crew member manned a position - they didn't just sit inside and wait to dismount.

The A7V design was influenced by the british design and then even made bigger, with the goal to create a large platform that could basically serve as a rolling/armed fortress.

Initially, since the Germans were mainly on the defensive after their Verdun offensive, German departments and the leadership didn't really think that there was a need for a complex offensive platform/weapon. The British tanks could also be knocked out with field/infantry guns or even stalled/knocked out with bundled hand grenades, so - after the first shock - the German government thought that tanks would not be a successful platform, for quite a while.

This resulted in several departments only slowly starting to pay attention to the new type of vehicle/weapon. The departments' commitments were confused and partly even half-assed.
Still, the Verkehrstechnische Prüfungskommission (= traffic engineering assessment commission, short VPK) was pressured by the OHL (the Army's Supreme Command) to develop a tank in October 1916, where then the VPK explored possibilities with German corporations and car manfacturers. The authority over the coordination of those efforts happened to end up in the Abteilung 7. The department was then tasked with the construction of a tank under the code name A7V in November, 1916. The wooden 1:1 scale model was finished on January 16, so development/design had just taken ~8 weeks.

Unsurprisingly A7V was work of a transport department.

So, we have British navy with Landships, Estienne, the artilleryman with assault guns and German transport department with IFVs.

The designation "Verkehrswesen" (common translations and usages would be "traffic", "transportation", "traffic and communication" or "traffic system" and "transport system") did not mean that the subdivision no. 7 was a real/pure traffic or transportation department. One or another source claims that the department was founded to get the tanks built, where it then sounds like the "Verkehrswesen" designation was picked as code name for the tank development. On the other hand, Verkehrswesen also included all modern types of movement/ground vehicles or vessels, and the department was a subdivision of the war department, not a division of a civilian department.
Since the technology/the weapon was completely new to the german war admnistration, some subdivision of the war department had to be assigned to take care of the development.
In any case, you are drawing the wrong conclusion here.

The department then hired an engineer, Joseph Vollmer, who was an expert in car and truck development, and who had developed/invented the world's first truck-trailer combination ("road train") for AEG's car division NAG in 1903, the project was a cooperation of the body manufacturer Kühlstein and Vollmer, but who also developed a strong interest in tractor development.
Obviously, the engineer had the required expertise to develop large/heavy vehicles.

The fact that this particular department managed to come up with solid blueprints and with a 1st model quickly (some sources say that the first full-size wood model was developed/built within 6 weeks), does not mean that the vehicle was designed or meant to be a an APC or IFV, at all.
The experimental predecessor of the Mark I derived from a tractor. Technically, even the Mark I was still a tractor where then the engineers had built a crew compartment and gun sections around it.
The German engineer refined that concept and aimed to create a version that would offer more space for the crew (16 men), be able to support troops and knock out enemy tanks.
Since each the engineer and the Army insisted on a number of specifications, like the retractable commander compartment, which was demanded by the Army to allow relocation on trains (bridges/tunnels), and other complex features and revisions, the completion of an operational prototype was signific. delayed (until October 1917).

The development of the K-Wagen had even started before the A7V development. The K-Wagen was a real monster (120 tons, even 150 tons at one development stage), and it looked like a giant Mark I.
1 production version was finished and was almost delivered by the end of the war, with a 2nd vehicle finished but lacking the engines. After the armistice, the provisional German government then asked for a permit to test drive the operational monster, but the Allies denied the request and ordered to scrap both vehicles.
One of the German light tank projects (the LK III, 1918) picked up the French approach, its predecessor LK II (1918) used parts of a civilian Daimler passenger car, and the first version LK I actually used the complete chassis of a civilian Daimler car. The tracks and some other features were rather copies of the successful British Whippet tank. All tanks were designed by Vollmer.

When the training of the crews for the first 5 A7V vehicles commenced (1918), coordination with infantry advances was part of the training.
The tank was designed to support the infantry but also to fight enemy tanks: In history's first tank battle (against british tanks) a tank of the 2nd AV7 Abteilung encountered 3 Mark IV tanks, 2 female versions and one male version, where it "knocked out" (heavily damaged) the 2 females but failed to attack/recognize the male Mark IV, which then hit the A7V so precisely, that the crew left the A7V. The male Mark IV was knocked out by direct German artillery fire eventually, iirc.
 
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ahmedreda

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Parts of the crew left the tank, but they had to abandon their assigned positions/guns in the tank to do that. There was no room to carry infantry sections and the crew consisted of a number of specialists: artillery gunners, MG gunners, loaders, driver, machinist(s), commander. All had infantry training ofc, but the tank was not designed to ferry "tankborne" inf troops, and each crew member manned a position - they didn't just sit inside and wait to dismount.

The A7V design was influenced by the british design and then even made bigger, with the goal to create a large platform that could basically serve as a rolling/armed fortress.

Initially, since the Germans were mainly on the defensive after their Verdun offensive, German departments and the leadership didn't really think that there was a need for a complex offensive platform/weapon. The British tanks could also be knocked out with field/infantry guns or even stalled/knocked out with bundled hand grenades, so - after the first shock - the German government thought that tanks would not be a successful platform, for quite a while.

This resulted in several departments only slowly starting to pay attention to the new type of vehicle/weapon. The departments' commitments were confused and partly even half-assed.
Still, the Verkehrstechnische Prüfungskommission (= traffic engineering assessment commission, short VPK) was pressured by the OHL (the Army's Supreme Command) to develop a tank in October 1916, where then the VPK explored possibilities with German corporations and car manfacturers. The authority over the coordination of those efforts happened to end up in the Abteilung 7. The department was then tasked with the construction of a tank under the code name A7V in November, 1916. The wooden 1:1 scale model was finished on January 16, so development/design had just taken ~8 weeks.



The designation "Verkehrswesen" (common translations and usages would be "traffic", "transportation", "traffic and communication" or "traffic system" and "transport system") did not mean that the subdivision no. 7 was a real/pure traffic or transportation department. One or another source claims that the department was founded to get the tanks built, where it then sounds like the "Verkehrswesen" designation was picked as code name for the tank development. On the other hand, Verkehrswesen also included all modern types of movement/ground vehicles or vessels, and the department was a subdivision of the war department, not a division of a civilian department.
Since the technology/the weapon was completely new to the german war admnistration, some subdivision of the war department had to be assigned to take care of the development.
In any case, you are drawing the wrong conclusion here.

The department then hired an engineer, Joseph Vollmer, who was an expert in car and truck development, and who had developed/invented the world's first truck-trailer combination ("road train") for AEG's car division NAG in 1903, the project was a cooperation of the body manufacturer Kühlstein and Vollmer, but who also developed a strong interest in tractor development.
Obviously, the engineer had the required expertise to develop large/heavy vehicles.

The fact that this particular department managed to come up with solid blueprints and with a 1st model quickly (some sources say that the first full-size wood model was developed/built within 6 weeks), does not mean that the vehicle was designed or meant to be a an APC or IFV, at all.
The experimental predecessor of the Mark I derived from a tractor. Technically, even the Mark I was still a tractor where then the engineers had built a crew compartment and gun sections around it.
The German engineer refined that concept and aimed to create a version that would offer more space for the crew (16 men), be able to support troops and knock out enemy tanks.
Since each the engineer and the Army insisted on a number of specifications, like the retractable commander compartment, which was demanded by the Army to allow relocation on trains (bridges/tunnels), and other complex features and revisions, the completion of an operational prototype was signific. delayed (until October 1917).

The development of the K-Wagen had even started before the A7V development. The K-Wagen was a real monster (120 tons, even 150 tons at one development stage), and it looked like a giant Mark I.
1 production version was finished and was almost delivered by the end of the war, with a 2nd vehicle finished but lacking the engines. After the armistice, the provisional German government then asked for a permit to snaptube vidmate test drive the operational monster, but the Allies denied the request and ordered to scrap both vehicles.
One of the German light tank projects (the LK III, 1918) picked up the French approach, its predecessor LK II (1918) used parts of a civilian Daimler passenger car, and the first version LK I actually used the complete chassis of a civilian Daimler car. The tracks and some other features were rather copies of the successful British Whippet tank. All tanks were designed by Vollmer.

When the training of the crews for the first 5 A7V vehicles commenced (1918), coordination with infantry advances was part of the training.
The tank was designed to support the infantry but also to fight enemy tanks: In history's first tank battle (against british tanks) a tank of the 2nd AV7 Abteilung encountered 3 Mark IV tanks, 2 female versions and one male version, where it "knocked out" (heavily damaged) the 2 females but failed to attack/recognize the male Mark IV, which then hit the A7V so precisely, that the crew left the A7V. The male Mark IV was knocked out by direct German artillery fire eventually, iirc.
Mechanized infantry ride in armored vehicles, which are expected to protect the occupants from small arms fire and shrapnel at least. These can be Armored Personnel Carriers, which typically lack much firepower of their own and need to dispatch the infantry to actually fight, or they can be Infantry Fighting Vehicles, which can lay down heavy firepower with autocannons or guided missiles and assault enemy positions without the infantry dismounting, or operate as a separate combat element from the infantry they carry.
 

GoodGuy

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Mechanized infantry ride in armored vehicles, which are expected to protect the occupants from small arms fire and shrapnel at least. These can be Armored Personnel Carriers, which typically lack much firepower of their own and need to dispatch the infantry to actually fight, or they can be Infantry Fighting Vehicles, which can lay down heavy firepower with autocannons or guided missiles and assault enemy positions without the infantry dismounting, or operate as a separate combat element from the infantry they carry.

Welcome.
The part of the discussion you quote was about the A7V and Perturabo's suggestion that the German tank was an infantry transport vehicle (which it wasn't), so I am not quite sure why you are stating unrelated facts about modern equipment.

Since tanks could not occupy/hold captured territory in 1916, infantry had to be brought forward (or follow the tanks) to actually clean/occupy the territorial gains. So while the Brits had built a breakthrough weapon that could remove barbed wire, obstacles and enemy gun positions, infantry troops were still unprotected during their advances. The British experimented a bit and tried to use stretched Mark V tanks as troop carriers, but these tests had to be aborted, because the small space and the lack of fresh air made even short distances unbearable for the soldiers.
Even though the German tanks offered somewhat more space, the Germans made no serious attempts to convert them to troop carriers, as they deemed the MG gunner positions necessary (since the tank had only one main gun - in the front). The low production numbers wouldn't have supported a general use as armored troop carriers, anyways.

Several sources state that the German OHL also ordered 90 unarmored supply versions (same chassis + engine, called "Überlandwagen"), which were then supposed to be used as all-terrain supply vehicles, some were completed, but they were very rare:
45703586551_84860e2df7_b.jpg


The Germans employed captured British and French tanks in two of their 3 Abteilungen, due to the lack of tanks/resources.

In turn, the British Mark IX can be seen as one of the world's first (if not the first) dedicated armored troop carrier:

British_Mark_IX_Armoured_Personnel_Carrier.jpg


For the Mark IX, the engineers had removed all unnecessary parts from the inside and had then mounted them on the outside (tubes, air intakes, etc. I guess). The engine was moved from the middle to the front of the vehicle. All these measures created a space that could carry 30 soldiers. That space was divided by the rotating transmission shaft, though, and the soldiers had to stand the whole time, so this was a rather tricky environment for the troops, actually. The crew was reduced to 4 men (driver, commander, machinist, MG gunner). The Mark IX was considerably slower than the Mark VIII, the top speed was 7 km/h only.
The attempts with a stretched Mark V were unsuccessful, it proved to be unsuitable for troop transport.
 
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