There were three type of battles in Europe in the Middle Ages:
There were two types of soldiers in Europe in the Middle Ages:
- and infantry.
Infantry tended to not be used in raids, because horses had the advantage in speed and mobility.
Cavalry were not much use in sieges, but when infantry were not available, the cavalry could obviously dismount.
Later in the Middle Ages, infantry began using CrossBows, which were easy to use, and effective in sieges. And so, when infantry were available for sieges, they would often use CrossBows, and would often be Mercenaries.
In set-piece battles, cavalry and infantry could work together.
For instance cavalry could not charge infantry that were in tight formation with spears. But cavalry were useful for attacking the enemy's flanks, and for pursuit in the case of a rout. However, for economic reasons, most field battles were fought between cavalry because it was too expensive to muster both cavalry and infantry most of the time.
The Crusades demonstrate that although most field battles in Europe during the Middle Ages were fought between Cavalry, the warriors of that age were capable of more sophisticated tactics.
Here it should be noted, that because lands to the East tended to be more arid, the opponents fighting against the European Crusaders were more skilled on horseback and with the bow and arrow. Eastern-style fighting was much more cavalry-oriented.
What tipped the scale in favour of the Crusaders in certain battles that they won, was the fact that the CrossBow could outrange the bow-and-arrow.
So, the Crusaders would line up infantry with edged-weapons in front, behind them would be CrossBow Infantry, with Cavalry protecting the flanks. The edged-weapon infantry would protect the CrossBowMen, who would shoot over the top and protect the edged-weapon infantry from enemy harrassment.