From 1861 to 1934, prisoners were kept at the Pacific Branch, U.S. Military Prison and Disciplinary Barracks on Alcatraz Island. The U.S. Army sent troublesome soldiers, including thieves, drunks, and deserters, there for confinement and rehabilitation, while the government also imprisoned enemies ranging from Confederate spies to Native American rebels to Hindu-German conspirators. During World War I, conscientious objectors were kept on the island. Soldiers guarding the island compelled prisoners to perform hard labor such as smashing rocks, building roads, and expanding the prison complex, and in the early 1900s the Army enlarged the prison and replaced many of Alcatraz's original fire-prone facilities with permanent concrete buildings. When prisoner populations grew large, other army forts around the Bay used the surplus labor. In the late 19th century, soldiers also imprisoned aggressive American Indian leaders who opposed the government's reservation policies, seizure of ancestral lands, and forced assimilation, as well as passive Indian resisters from the Paiute, Hopi, and other tribes, separating them from their families, bringing them to Alcatraz, and trying to coerce them into conforming to white culture.
