(1) Land troops (land forces) on a level with a naval fleet.
(2) Totality of armed forces of a state.
(3) Large operational unit designated for the conducting of operations.
In the 18th and first half of the 19th centuries the term “army” meant troops united under a single command in one theater of operations, hence the names Rhine Army, Danube Army, and so on.
The growth in numbers of national armed forces, the difficulty of controlling troops located along a broad front and operating in different directions, and the appearance of new factors which influenced the conduct of battles (the railroad, and in the 20th century first automobile and then air transport) made it necessary to create individual armies within a single theater of operations. Instead of one army carrying out a strategic task throughout the whole theater, a number of armies appeared, each under the command of one person (the commander of the army), and each representing a large operational unit of troops intended to carry out the individual operational tasks in the theater. The army had a headquarters staff and the necessary logistic agencies; it was usually designated by an ordinal number. Such individual armies in a single military theater appeared in Russia before the Patriotic War of 1812, when all the forces were divided into three armies. In 1812, Napoleon, too, began to organize individual armies (groups); previously he had made all the corps directly subordinate to himself. Later, individual armies appeared in Prussia (1866), Japan, (1904–05), and other states. During World War I, Russia had 13 armies (1916), Germany had 15 (1918), and France had ten (1918). During the Civil War (1918–1920) a new type of army unit—the mounted army—appeared in the Soviet Armed Forces.
Initially, armies did not have a permanent organization; their composition was determined by the tasks they carried out, the characteristics of the military theater, the strength of the enemy, the existing possibilities for security of troop control, and other conditions. Beginning with the 19th century, armies generally consisted of three to six or more corps, and corps consisted of two to four divisions. In the Civil War the Soviet Army had no corps; it was made up directly of divisions. In addition to corps (divisions), armies included various auxiliary units. The numerical composition of armies was not constant: thus, the Russian First Army numbered 127,000 men in 1812, and the Second Army 40,000 men; the Prussian First Army numbered 140,000 men in 1866, the Second Army, 115,000 men; in 1916 the Russian Eighth Army included 225,000 men, the Ninth Army, 165,000 men. In the Great Patriotic War (1941–45), German fascist armies included 120,000–250,000 men; Soviet armies numbered 60,000–100,000 men.
Before the appearance of automobiles, automatic weapons, airplanes, and tanks, the foundation of the army was infantry, cavalry, and artillery. The shock force of the army was based on bayonets, its maneuverability on the mobility of the infantry (25–30 km in a 24-hour period). Armies of World War I and Soviet armies of the Civil War were of a transitional type. They were distinguished from previous armies primarily by the increased saturation of war matériel—that is, automatic weapons, mortars, and guns—and the appearance of an air force, armored-vehicle troops, chemical troops, antiaircraft defense troops, motor transport units, road units, and other units. The cavalry did not lose its importance. However, these armies were nonetheless unmounted armies with an inherently low level of maneuverability. The infantry and artillery constituted the basic shock force. Tanks, planes, and motorized transport were not widely employed; they had not been perfected technically and thus could not fundamentally alter combat capabilities.
By the start of World War II (1939–45) the engine and the combat vehicle had become prominent in the armies of developed states. Tank armies (in the USSR and Germany), airborne armies, and air armies appeared in World War II along with combined arms armies. The combat strength of combined arms armies had become more varied than that of the period of World War I. In addition to infantry (rifle) units, they began to include tank and mechanized (motorized) units. On the Soviet-German front the composition of combined arms armies fluctuated from three to five army corps (ten to 16 infantry divisions) and from two to eight tank and motorized divisions. Soviet combined arms armies had from three to five infantry corps (nine to 14 divisions) and one or two tank (mechanized) corps. The German tank army consisted of two or three tank corps. The Soviet tank army usually consisted of three corps (one or two mechanized and one or two tank corps). Combined arms and tank armies had a great number of different means of reinforcement. The American and British forces had no tank armies.
After World War II, the army as a large operational unit of troops developed further as a result of the combat experience that was acquired, the rearmament of troops with the new combat technology, the mechanization and motorization of troops, and the appearance of rocket troops in the 1960’s.
I. S. LIAPUNOV