Just to clarify, from what I have read most of the time the armor division would achieve a breakthrough and then the allies would either have to retreat or reinforce their position often they would retreat but sometimes they would be push back by infantry on some section of the frontline. This made me curious as it presented a dilemna either the german suffer heavy casaulties assaulting with just infantry or they would have to keep their infantry divisions static and let the tanks do the work which would take a really long time which is not the case since poland fell in a month and france in 6 weeks.