From: Vermont, USA
Just to elaborate on a couple of points, the game does track manpower for each nation and each unit has a manpower cost, so while units are rated in strength points, they also very much have an impact as far as the cost to raise them and replace casualties. This eventually affects your economy and losses will affect your national morale as well. There's a balancing act required to both have enough forces to cover the fronts you need to cover, replace losses, research new techs, recruit new units, etc. It can be easy to get in trouble if you are not careful and over-build or over-focus in one area or another.
Also, the AI is instantaneous for me. I finish my turn and watch it do its turn, no wait while it's thinking.