This chapter looks at the nature of warfare in our period and at some of the significant wars that occurred within it. Warfare was an important fact of life for many in this period, and it had different impacts depending on status, gender and geographical location. Sieges and siege warfare affected the physical appearance of cities and castles, and the impact can still be seen in the defensive development in the walls, towers and gates of many medieval towns, cities and castles. The art of siege warfare was a popular topic in literature of the period, which covered both contemporary and ancient sieges. Set piece battles litter both the geographic spread of Europe and any timeline of the period. Infantry soldiers were cheaper to hire or equip than the fully mounted knights, and this was a consideration in a period when there was a movement from feudal hosts to armies of paid soldiers.