That irritated me when I was playing as France, because I had no connection of land to the Soviet Union all the land I captured went to Holland. But if I didn't go on the offensive the Soviet Union would have crushed Europe.
CC, you want to be aiming for at least 60 infantry divisions and the more, the better. They will follow your armoured divisions in and secure the land you gain. I, personally, never mix armoured and infantry divisions together in the same Corps. My mixes are almost always two armoured and one motorised (or mechanized) infantry in each Corps of three divisions. I did have an armoured army though as America that had nine armoured divisions.
I'm not having much time to play it recently, nor am I having much time to read "Bomber Crew" - it's all quite irritating.