Prologue: high-medieval tactics

Although revisionist historians have lately argued otherwise, in the High Middle Ages (c. 1000–1300) cavalry was the dominant arm in battle. Infantry was valued, and was present at most battles, but its role was often almost purely defensive, and it usually takes offensive action to win a true victory. As Jim Bradbury observed in concluding his study of Anglo-Norman battles (in which dismounted knights played a substantial role), the biggest threat on the battlefield was a cavalry charge, but the strongest defence against a head-on mounted attack was a steady line of spear-armed footmen supported by archery. In other words, cavalry and footmen could work together like sword and shield. A swordsman surely values a sturdy shield, and even knows it can sometimes be used to strike important blows, but would sooner dispense with it than try fighting without his blade.

Battles in this period tended to follow one of a few basic patterns. Often the opposing armies would face off, infantry-line to infantry-line, each with its cavalry to the flanks or rear. Then the mounted forces would charge each other at a trot, while the footmen either held their ground or advanced to contact very slowly, so that they could keep their order. Since the former closed much more quickly, and since mounted combat was typically decided more rapidly than a contest between shield walls, the issue of the battle as a whole was likely to be determined by the cavalry fight.