Pago Pago was a vital naval base for the U.S. during World War II. Limited improvements at the naval station took place in the summer of 1940, which included a Marine Corps airfield at Tafuna. The new airfield was partly operational by April 1942, and fully operational by June. On March 15, 1941, the Marine Corps' 7th Defense Battalion arrived in Pago Pago and was the first Fleet Marine Force unit to serve in the South Pacific Ocean. It was also the first such unit to be deployed in defense of an American island. Guns were emplaced at Blunts and Breakers Points, covering Pago Pago Harbor. It trained the only Marine reserve unit to serve on active duty during World War II, namely the 1st Samoan Battalion, U.S. Marine Corps Reserve. The battalion mobilized after the attack on Pearl Harbor and remained active until January 1944.