I'm a huge fan of the Total War series and have spent more hours than I'd like to admit conquering the virtual world. As I was playing Medieval II earlier today, I thought about the fact that the game organises armies into units of spearmen, axemen, archers etc. How common was this in real life? Ie. would a Medieval king or general have a certain number of men with spears acting as one unit, another group of men with axes acting as a unit of axemen etc.? Or would it be more common to have groups of soldiers armed with various melee weapons forming a rough mob of soldiers?
The short answer is that while we don't know an awful lot about the details of medieval military organization, small units were not segregated beyond their tactical role, and were probably formed more based on geographic or political origin: ie, Lord Thomas's company of infantry, Earl Henry's conroi of knights, Captain John's archers. We have no source evidence that swordsmen, axemen and spearmen were formed into their own special units.
You may find these past answers of mine enlightening: