The name "brigade" is something of a misnomer, as there were several American battalions organized under the Fifteenth International Brigade of the Spanish Republican army. This brigade was loosely organized by the Comintern and was made up of volunteers from nations around the globe. The George Washington Battalion, Abraham Lincoln Battalion, and John Brown Battalion were the American contingent. The name Abraham Lincoln Brigade was adopted by stateside advocates.
Most of the people making up the Abraham Lincoln Brigade were official members of the Communist Party or affiliated with other socialist organizations. The IWW, or "Wobblies", were also strongly represented. However, the brigade was made up of volunteers from all walks of American life, and from all socio-economic classes. It was the first racially integrated American fighting force, and the first to have an African-American officer, Oliver Law, lead white soldiers.
American volunteers began organizing and arriving in Spain in 1936. Centered in the town of Figueras, near the French border, the brigade was organized in 1937 and trained by Robert Merriman. By early 1937, its numbers had swelled from an initial 96 volunteers to around 450 members.
The International Brigade was used by the Loyalist army for several battles in Spain. They unsuccessfully defended the supply road between Valencia and Madrid in the Jarama Valley from February 1937 until June 1937. They were also present at the battles of Brunete, Saragossa, Belchite, and Tereul.
The Brigade was a cause celebre in the United States, however. Liberal and socialist groups organized fund-raising activities and supply drives to keep the Brigade afloat. News of the Brigade's high casualty rate and bravery in battle made them romantic figures to an America concerned about the rise of Fascism around the world.
The war dragged on and the Fascist forces gained victory after victory over the Spanish Republic. The International Brigade was withdrawn from battle by the Spanish prime minister in spring of 1938. Most of the surviving Lincolns were repatriated promptly afterwards, and were welcomed home as heroes.
The legacy of the Lincoln Brigade has been a romantic vision of idealistic volunteers fighting for justice and freedom in a nation far from their own.