Army

A U.S. Army soldier firing a 5.56 mm round from an M4 rifle (the M4 also has an M203 Grenade Launcher attached).

An Army is a term either referring to the largest type of formation for a land-based military force, or the entirety of a nation's military force responsible for its land defenses, both of which are composed of soldiers, trained to engage in war.

An army, as a single in-theater force, operates at a strategic level, but is composed of and often divided into smaller operational units which operate at a tactical level. It is also characterized by a command hierarchy utilizing ranks (divided between officers and enlisted, but often with a non-commissioned officer corps as well), with a rigid adherence to protocol and chain of command necessitated by the conditions of war.