<P> In times of war , the Coast Guard or individual components of it can operate as a service of the Department of the Navy . This arrangement has a broad historical basis , as the Coast Guard has been involved in wars as diverse as the War of 1812 , the Mexican -- American War , and the American Civil War , in which the cutter Harriet Lane fired the first naval shots attempting to relieve besieged Fort Sumter . The last time the Coast Guard operated as a whole within the Navy was in World War II . More often , military and combat units within the Coast Guard will operate under Navy or joint operational control while other Coast Guard units will remain under the Department of Homeland Security . </P>
when was the last time the coast guard was part of the navy
World War II