Bill,
Thanks for your post.
This usually happens when a force believes it has achieved the objective. Now remember in most cases this means simply having a ten to one ratio within the obj perimeter. There is no annotation on your screen dump, so it is hard to see where the attack objective was. I'm assuming it is the crossing. If so then you already have a friendly unit defending there. The only other enemy nearby is the 5.89 but I have no indication of how strong that unit is. I suspect it is weak and not able to affect the odds enough.