The United States Department of Justice acquired the United States Disciplinary Barracks, Pacific Branch, on Alcatraz in 1933. The island was then adapted and used as a prison of the Federal Bureau of Prisons in August 1934, after the buildings were modernized and the security was greatly increased. Given this high security and the island's location in the cold waters and strong currents of San Francisco Bay, prison operators believed Alcatraz to be escape-proof and America's most secure prison. They were wrong.