The Partisans had operated many small boats in raids harassing Italian convoys in the Adriatic Sea during World War II. After the war, the navy operated numerous German and Italian submarines, destroyers, minesweepers, and tank-landing craft captured during the war or received as war reparations. The United States provided eight torpedo boats in the late 1940s, but most of those units were soon obsolete. The navy was upgraded in the 1960s when it acquired ten Osa-I class missile boats and four Shershen class torpedo boats from the Soviet Union. The Soviets granted a license to build eleven additional Shershen units in Yugoslav shipyards developed for this purpose.