Well, don't take my word for it, but it really depends on who's raising the army. In the 12th and 13th centuries, there were no professional standing armies, only levied forces that went and fought and then were disbanded once the fighting was over. The king would say to his vassals, "Hey I'm going to war, help me." The vassals would comply and say to their vassals, "The king is going to war and he needs help. Muster your troops and help me." Now it matters who is raising it because if you want a big army, you need either a lot of money or a lot of land. So if a character is a powerful duke, then of course he'll be able to muster a sizable force. But, if the character is a count or a baron or whatever, then he might only be able to raise a small or medium force. As for the actual numbers at that time, I would say maybe 6000-8000 or 10000 men in total. If a large realm is going to war, the king would probably be able to raise about 10000 men if all of his vassals gathered into one huge force. An average-sized realm would likely be in that 5000-8000 area, and a smaller realm, perhaps a petty kingdom, would be able to raise even less. I don't believe there are solid numbers on exact troop types, but there would likely be a lot of light infantry (spearmen, not archers), a good amount of archers and crossbowmen, the heavy infantry would be limited to either knights who fight dismounted (not many did), mercenaries, or just well off people that could afford good equipment (everyone bought their own equipment). For cavalry, honestly I'm not sure how many light cavalry and heavy cavalry there would be, but I would guess that there might be a few hundred knights on average and maybe a few hundred light cavalry as well. Horses were expensive, so there wouldn't be any peasant cavalry, but there might be experienced sergeants who can afford horses and light cavalry mercenaries. By the way, most of the army used spears, axes, and knives, and wore either just their clothes or some padded armor such as a gambeson (padded armor is not bad, it is EXTREMELY good; do not underestimate it). The knights and the richer folk were the ones with the metal or otherwise more expensive armors. I hope this helps, since I too write stories in and about the Middle Ages and sometimes the information about this era is very confusing and unclear. I hope it all goes well for you. :)

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