@Wolfie88: About your 3th solution:The reason why I always need to save game many times again and again during one match round is my computer is so poor at gaming,my computer often crashed during a fantastic match,to avoid wasting my previous playing time & lose my striving during one game match,I have to save game many times again & again.
And Why I need 300 to 500 popcap is because if I play win condition as Annihilation,then I have to annihilate almost all of the enemy units(including enemy structures) to win a match,but,if I play win condition as Victory Point,then I think 195 to 250 popcap is enough because in this mode,I only need to keep the front-line not to be destroyed,then I will win the game.And one more thing I want to notice you is that I think no matter what the two kinds of win condition is,on this map,Germany always need less population cap than Allies to win the war,just because Germany has very strong defense system in this Day-D map and there are only two narrow roads for engaging!About my situation: I have experienced play as German with Victory Point succesfully,but now,I want to simulate the Allies in those historical years:not just fight for few Victory Point,but aliies need to gradually go deep into heart of german area and annihilate all of the recalcitrant german they encounter.So,I recently play as allies,win condition is Annihilation,so,I need larger popcap to ensure allies could annihilate all threats on german's highland.