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. Marcus Furius Camillus is traditionally regarded as the great organizer of the legion. Under Camillus the hoplites were divided into three groups: the hastati (youngest men), the principes, and the triarii (oldest). Within the legion was the cohort, consisting of one maniple of each of the three groups plus 120 velites and a cavalry unit about 30 strong. A legion was composed of 10 cohorts and comprised about 5,000 men. In Caesar's time each legion had a commander who was responsible to the Senate, 6 tribunes, a legate, a prefect, and some 60 centurions. Training was hard, with much difficult drilling to prepare the men especially in shock tactics and for rapid marches. The standard weapons were the spear (pilum) and (after Scipio Africanus Major conquered Spain) the short thrusting sword (gladius). The characteristic emblems of the legions were eagles inscribed SPQR [Senatus Populusque Romanus—the Senate and the people of Rome], and they carried the eagles in triumph over the far reaches of the empire for hundreds of years. Upon the legions rested to a large extent the glory of Rome. They were primarily heavy infantry and were vulnerable to quickly moving cavalry and archers (e.g., the defeat of Marcus Lucinius Crassus at Carrhae) and to guerrilla fighters (e.g., the famous defeat of Varus by the Germans). With the Germanic invasions the legion proved unable to match the barbarian horsemen, rendering it obsolete.

Legion of Honor: see decorations, civil and military.

Foreign Legion, French volunteer armed force composed chiefly, in its enlisted ranks, of foreigners. Its international character and the tradition of not revealing enlistees' backgrounds have helped to surround the Foreign Legion with an aura of mystery and romance. Although foreigners had served in French armies previously, King Louis Philippe created (1831) this specific foreign legion. Originally intended to pacify Algeria, the legion also was active in the pacification of Morocco and fought in other areas of the French colonial empire and in both world wars. It was later active in the French campaigns in Indochina and Algeria. One regiment of the legion supported Algerian insurgency against the French government (1961) and was rapidly disbanded. The legion was normally stationed in Algeria until 1962, when its headquarters were transferred to S France, near Marseilles. The army's regiments were scattered throughout the world. There have been many other foreign legions; e.g., a British legion participated in the Carlist Wars in Spain, and in the Spanish civil war (1936-39) the International Brigade fought on the Loyalist side.

Czech Legion, military force of about 40,000 to 50,000 men, composed mostly of Czech and Slovak Russian prisoners of war and deserters from the Austro-Hungarian army who enrolled in the Russian army during World War I. Constituted with the consent of the Russian revolutionary government set up in 1917, the legion took a minor part in fighting the Germans and Austrians. After Russia left the war as a result of the peace of Brest-Litovsk in 1918, an agreement between the legion and the Bolshevik regime in Russia allowed for the evacuation of the legion via the Trans-Siberian RR and its eventual transfer to the Franco-German front. During its evacuation, the legion reluctantly became involved in the Russian civil war, fighting mostly on the anti-Bolshevik side, and controlled in mid-1918 much of the vital railroad line. However, plans (favored by some Allied officials) to use the legion for intervention against the Soviet regime never materialized.

American Legion, national association of male and female war veterans, founded (1919) in Paris. Membership is open to veterans of World Wars I and II, the Korean War, and the Vietnam War. The preamble to the organization's constitution, adopted at the convention in St. Louis that same year, expresses its purposes in part as "to uphold and defend the Constitution of the United States; to maintain law and order; to foster and perpetuate a one hundred percent Americanism; … to safeguard and transmit to posterity the principles of justice, freedom, and democracy; to consecrate and sanctify our comradeship by our devotion to mutual helpfulness." The organization has done much work in social welfare, particularly in the areas of veterans' benefits and child care. With national headquarters in Indianapolis, Ind., it is the largest veterans' association; it holds an annual convention, which often addresses national issues. The American Legion's efforts have been bent not only to obtaining benefits for veterans but also for the families of those who died in war. Although it is organized on a nonpartisan, nonpolitical basis, its policies have been criticized as extremely conservative by many opponents, and its influence has waned, particularly with the loss of many World War II veterans. There is also a women's auxiliary for the wives, mothers, sisters, and daughters of veterans.

Military organization, originally the largest permanent unit in the Roman army. It was the basis of the military system by which imperial Rome conquered and ruled its empire. The early Roman Republic found the Greek phalanx too unwieldy for fragmented fighting in the hills and valleys of central Italy. To replace it the Romans evolved a new tactical system based on small and flexible infantry units called maniples. These were grouped in larger units called cohorts, which ranged from 360 to 600 men, depending on the era. Ten cohorts made up a legion, which moved into battle with four cohorts in the first line and three each in the second and third lines. Seealso Foreign Legion.

Learn more about legion with a free trial on Britannica.com.

Organization of U.S. war veterans. Founded in 1919, it works for the care of disabled and sick veterans and promotes compensation and pensions for the disabled, widows, and orphans. Nonpolitical and nonsectarian, its membership requirement is honourable service and an honourable discharge. It was instrumental in establishing veterans' hospitals, and it sponsored the creation of the U.S. Veterans Administration in 1930. In 1944 it played an important role in the passage of the GI Bill. The American Legion claims about three million members in some 15,000 local posts, or groups.

Learn more about American Legion with a free trial on Britannica.com.