Despite the rise of knightly cavalry in the 11th century, infantry played an important role throughout the Middle Ages on both the battlefield and in sieges. From the 14th century onwards, there was a rise in the prominence of infantry forces, sometimes referred to as an "infantry revolution".
In the medieval period, the mounted warrior held sway for an extended time. Typically heavily armoured, well motivated and mounted on powerful, specially bred horses, the mounted knight represented a formidable force, which was used to effect against more lightly armoured troops. Since only the noble classes could afford the expense of knightly warfare, the supremacy of the mounted cavalryman was associated with the hierarchical structure of medieval times, particularly feudalism. As the period progressed, however, the dominance of the cavalry elite began to slowly break down. The Black Death in the 14th century swept through Europe, devastating the population and resulting in serious manpower shortages. This encouraged more economical use of available manpower, and the infantryman was much cheaper to outfit and maintain than the aristocratic knight. The Crusade era also saw a rise in the importance of infantry, and required large numbers of men and material to be organized for distant battlefields. Such expeditions were part of the growing number of sieges, disputes and campaigns throughout the 13th and 14th centuries that greatly increased the cost of warfare for medieval regimes. The relative inexpensiveness of the infantryman, combined with a shortage of manpower, provided incentives for expanding their use.
The most common infantry throughout the early medieval period were peasants and commoners who were obliged to fight for the local lord, due to their place in the feudal system. They were always unarmoured or lightly armoured and fought either with simple agricultural or hunting tools such as axes and long knives, or with a spear and shield. In most circumstances they were expected to bring and maintain their own equipment. At few times they were outfitted by the lord or king they fought for. These men were essentially conscripts and as such their discipline, morale and fighting ability varied greatly. Generally those fighting to protect their homeland were far more motivated than those fighting abroad.