army, large armed land force, under regular military control, organization, and discipline.

Ancient Armies

Although armies existed in ancient Egypt, China, India, and Assyria, Greece was the first country known for a disciplined military land force. The Greeks made military service obligatory for citizens and training was rigorous. As a result of Greek military successes, leaders of other nations sought the services of Greek mercenaries. In time, a class of professional soldiers developed. They sold their services to other rulers as well as to wealthy Greeks who chose to avoid required military service (see Xenophon Xenophon (zĕn`əfən), c.430 B.C.–c.355 B.C., Greek historian, b. Athens.
..... Click the link for more information. ).

Like the Greek armies, the Roman army was originally composed of citizen soldiers. As the Roman Empire expanded, a professional standing army came into being; it became increasingly composed of barbarian mercenaries. The Roman army was divided into legions legion, large unit of the Roman army. It came into prominence c.400 B.C. It originally consisted of 3,000 to 4,000 men drawn into eight ranks: the first six ranks, called hoplites, were heavily armed, while the last two, called velites, were only lightly armed.
..... Click the link for more information. , each of which included heavy and light infantry, cavalry, and a siege train. The army became a political force that often determined who ruled the empire.

Feudal Armies

In Islam, slave soldiers were often trained from youth to be loyal only to their owners. These slave armies often established dynasties of their own (see Mamluks Mamluk or Mameluke (măm`əlk) [Arab.
..... Click the link for more information. ; Janissaries Janissaries (jăn`ĭsâr'ēz) [Turk.,=recruits], elite corps in the service of the Ottoman Empire (Turkey).
..... Click the link for more information. ). In medieval Japan and Europe, samurai samurai (sä'mrī`), knights of feudal Japan, retainers of the daimyo .
..... Click the link for more information. and knights knight, in ancient and medieval history, a noble who did military service as a mounted warrior.

The Knight in Ancient History

In ancient history, as in Athens and Rome, the knight was a noble of the second class who in military service had to furnish
..... Click the link for more information. , respectively, owed military service to a lord. The European system depended on the feudal levy, which required knights and yeomanry to provide a fixed number of days of military service per year to a great lord. Because of this limitation on service and the poorly trained force that it produced, sustained military operations were difficult. Feudal armies were undermined by the development in England of the longbow, but they were destroyed by the introduction of gunpowder gunpowder, explosive mixture; its most common formula, called "black powder," is a combination of saltpeter, sulfur, and carbon in the form of charcoal. Historically, the relative amounts of the components have varied.
..... Click the link for more information. . Armed knights became easy victims of hand-carried firearms and castle walls could now be breasted by cannon.

Professionals and Conscripts

National armies, largely composed of mercenaries, reappeared after the introduction of gunpowder. An example is the Italian condottiere, who hired mercenaries to fight for the prince who was able to pay the most. German and Swiss mercenaries served all over Europe in the 15th and 16th cent. Professional soldiers were also a notable feature of the armies of the Ottoman Turks, who threatened to destroy the forces of Western Europe in the 16th cent. Eventually, as a result of the writings of such political theorists as Niccolo Machiavelli Machiavelli, Niccolò (nēk-kōlô` mäkyävĕl`lē)
..... Click the link for more information. , national or standing armies developed—armies of professional soldiers led mostly by officers from the country's aristocracy.

After the Thirty Years War (1618–48), France emerged as the preeminent European military power. Under Louis XIV and his war minister, the marquis de Louvois Louvois, François Michel Le Tellier, marquis de
..... Click the link for more information. , that country organized a national standing army that became the pattern for all Europe until the French Revolution. A professional body, set apart from civilian life and ruled under an iron discipline, the standing army reached harsh perfection under Frederick II of Prussia.

In the late 18th cent. the American and French revolutions brought about the return of the nonprofessional, citizen army. The introduction of conscription conscription, compulsory enrollment of personnel for service in the armed forces. Obligatory service in the armed forces has existed since ancient times in many cultures, including the samurai in Japan, warriors in the Aztec Empire, citizen militiamen in ancient
..... Click the link for more information. during the French Revolutionary Wars led to mass armies built around a professional nucleus. Officers could be from any class. Conscription also transformed non-European armies, such as that of Egypt during the early 19th cent.

The Modern Army

With the advent of railroads and, later, highway systems it became possible after the mid-19th cent. to move large concentrations of troops, and the nations of the world were able to benefit from enlarging their manpower bases by conscription. Armies changed technologically as well. Trench warfare trench warfare. Although trenches were used in ancient and medieval warfare, in the American Civil War, and in the Russo-Japanese War (1904–5), they did not become important until World War I.
..... Click the link for more information. resulted from improvements in small arms and prompted the development of various weapons designed to end the stalemates and murderous battles that entrenched forces produced. The growing role of artillery artillery, originally meant any large weaponry (including such ancient engines of war as catapults and battering rams) or war material, but later applied only to heavy firearms as opposed to small arms .
..... Click the link for more information. made logistics even more important. From the first, armies had needed soldiers to supply the fighting troops—even when the armies simply lived off the land. No formal distinction orginally was made between service troops and combat troops, but with the creation of the great citizen armies after the French Revolution formal specialization proliferated, and quartermasters, ordnance troops, engineers, and medical specialists were organized into separate units. The development of mechanized warfare mechanized warfare, employment of modern mobile attack and defense tactics that depend upon machines, more particularly upon vehicles powered by gasoline and diesel engines.
..... Click the link for more information. in the 20th cent. made armies powerful and highly mobile and yet did not always provide them with the capabilities needed to fight so-called asymmetric opponents, such as they face in guerrilla warfare guerrilla warfare (gərĭl`ə) [Span.
..... Click the link for more information. and terrorism terrorism, the threat or use of violence, often against the civilian population, to achieve political or social ends, to intimidate opponents, or to publicize grievances.
..... Click the link for more information. .

The term army is still applied to all the armed land forces of a nation, but it is also used to designate a self-contained unit with its own service and supply personnel. In many armies today the division (usually about 15,000 men and women) is the smallest self-contained unit (having its own service and supply personnel). Two or more divisions generally form a corps; and an army (c.100,000 men or more) is two or more corps. In World War II, army groups were created, including several armies (sometimes from different allied forces). Above the groups is the command of a theater of operations, which in the United States is under the control of the Joint Chiefs of Staff.

See Defense, United States Department of Defense, United States Department of, executive department of the federal government charged with coordinating and supervising all agencies and functions of the government relating directly to national security and military affairs.
..... Click the link for more information. ; strategy and tactics strategy and tactics, in warfare, related terms referring, respectively, to large-scale and small-scale planning to achieve military success. Strategy may be defined as the general scheme of the conduct of a war, tactics as the planning of means to achieve strategic
..... Click the link for more information. ; warfare warfare, violent conflict between armed enemies. In modern times warfare has usually been conducted by the armed forces (e.g., army, navy, and air force) of a nation or other politically organized group.
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Bibliography

See A. Vagts, A History of Militarism (1937); L. L. Gordon, Military Origins (1971); J. Keegan and R. Holmes, Soldiers (1986); R. O'Connell, Of Arms and Men (1989).

army

Large, organized force armed and trained for war, especially on land. The term may be applied to a large unit organized for independent action or to a nation's or ruler's overall military organization for land warfare. The character and organization of armies have varied through history. At various times armies have been built around infantry soldiers or mounted warriors (e.g., cavalry) or men in machines, and have been made up of professionals or amateurs, of mercenaries fighting for pay or for plunder, or of patriots fighting for a cause. See also air force, conscription, guerrilla, military unit, militia, U.S. Army.