Army

Army, land fighting force of a nation; more narrowly, a large unit of ground forces under a single commander. Primitive armies consisted of raiding parties that waged individual combat using stones and clubs. Later, horses and chariots increased the mobility of armies, while the development of artillery extended their range. Formation tactics evolved with the Macedonian phalanx and Roman legion. The 20th-century army depends upon technology. Because of the ongoing development of weapons and detection systems, modern armies must be highly mobile, a need that has blurred the traditional distinctions between army, navy, and air force. Nuclear weaponry has taken the range of firepower to its limits, and the value of tactical formations has largely been eliminated by radar, making unconventional units (guerrillas, paratroops) increasingly important.

See also: Army, U.S.