The United States Navy's O class submarines were created out of the lessons learned from the United States L class submarine. The O class were more robust with greater power and endurance for ocean patrols. The O class were built much faster than previous classes and were commissioned in 1918. The group 2 boats entered service just before the end of World War I. Eight of the group 1 boats survived to serve in World War II as training boats when they were recommissioned in 1941.