Infantry are troops that fight primarily on foot, with portable weapons. They may arrive on scene in various ways, and are deployed either in formations or as skirmishers and guerillas.
Infantry have been the core of most armies throughout history. In ancient times the most prominent formations were the phalanx and later the more sophisticated legion, which could reach several thousand men in size. After the Roman Empire collapsed cavalry dominated the west for a long time, but eventually infantry regained supremacy with the advent of gunpowder. They are often supported by armoured fighting vehicles, artillery, or aircraft but are the only type of troop that can take and hold ground. In modern warfare, mechanized infantry is the most commonly used type of infantry.