I've noticed this- for example, in STW, when you conquer all of Japan you may have something like 20,000 troops in your armies.. twenty FULL armies (armies are 960 men max.. maybe twice as big if you're playing with units of 120, I don't know). This may even be a bit on the high side.

Meanwhile, there were hundreds of thousands of troops on the battlefields in Japan! At Sekighara- the battle in 1600 (also the biggest battle in ancient Japan, I believe) that established the Tokugawa shogunate- there were around 220,000 alone. Altogether in Japan there must have been at least 300,000.

Thus I tend to look at each "man" in STW or MTW as ten men, just to keep things realistic. A loss of an army of one or two thousand men in Europe or Japan in the Medieval ages would hardly have given a leader pause, in many cases, whereas in our case in these games it can be a near catastrophe.