 Hohenzollern monarchical rule of Prussia ceased in 1918 after the fall of the German Empire in the aftermath of World War I; the Kingdom becoming instead the Free State of Prussia.The Allied Control Council decreed the formal abolition of the state of Prussia in 1947 following World War II.The Prussian national and merchant flag was originally a simple black-white-black flag issued on May 22, 1818, but this was replaced on March 12, 1823, with a new flag.