One of the best real time strategy games of all time incorporating huge numbers of men and fantastic battles is Rome: Total War in my opinion. Not only are the battles extremely fun, and managing the Roman Empire a satisfying feat, but the game is also very historically accurate (as far as computer games go).
What types of things can you learn from Rome: Total War? First of all, the general unit types of men. When the empire first started to form, there were three Roman families that became somewhat like factions. Each of these families had certain types of troops at their disposal. This included the Triarii, the Principes, and the Hastati. The game accurately shows this as troops you can recruit in your cities for battles. They all have their abilities and strengths, and they are proportional to what they were historically. Also, the game accurately reflects the major changes in the Imperial Roman Army when the Marius Reforms came to be. Though it may not happen in the right year (in the game it depends on how fast you develop), the changes that happen are accurate. Another thing you can learn from the game is the battle dress of what the Roman legionnaires wore.
The cool thing about the game is that you can zoom down into the battle field pretty far and take a close look at the soldiers. The legions all have lorica segmentata on them, scutums (Roman shields), and fantastically accurate Roman helmets. The helmets change from the troopers to the Praetorian Guard, to the general on the battle field. The Roman helmets are pretty detailed and you can see how the designs changed. You can also see them throw pilum (a spear like weapon), which was thrown as the enemy came close. Though the graphics don't allow for incredible detail on the pilum, you get the general idea.
John Hilde is a historical weapons and armor collector and owns his own online store selling authentic armor and weapons. Please visit http://www.armorvenue.com to learn more.