V5 rules, the infantry playthrough on page 165. It has the German player roll for smoke - and it basically says … they roll a 2, giving a successful placing of the smoke marker. The German impulse is not over. The example then goes on to move the squad at -1 MF.
The term 'impulse is not over' due to success, implies that failure of the same would mean the impulse IS over. I have always played it that way.
Also the spotting rule goes out of its way to show that failure of a spot alone does not use the impulse - other rules including smoke do not say that. So the rules taken at face value have spotting as the EXCEPTION to impulse conclusion.
