(Indonesia) and then the Spanish—reached the Carolines in the sixteenth century, with the Spanish establishing sovereignty. It was sold to Germany in 1899, conquered by Japan in 1914, before being seized by the United States during World War II and administered by the US under United Nations auspices in 1947 as part of the Trust Territory of the Pacific Islands.During World War II, a significant portion of the Japanese fleet was based in Truk Lagoon. In February 1944, Operation Hailstone, one of the most important naval battles of the war, took place at Truk, in which many Japanese support vessels and aircraft were destroyed. On May 10, 1979, four of the Trust Territory districts ratified a new constitution to become the Federated States of Micronesia. Palau, the Marshall Islands, and the Northern Mariana Islands chose not to participate. The FSM signed a Compact of Free Association with the United States of America, which entered into force on November 3, 1986, marking Micronesia's emergence from trusteeship to independence. The Compact was renewed in 2004.