Spain lost Guam during the 1898 Spanish–American War in a bloodless invasion. For the next forty years, the United States Navy assumed executive control of the island, treating it more as a military outpost than an overseas territory, with little to no civilian say in the island's affairs. Governor Captain Willis Winter Bradley instituted the Guam Congress during the 1930s as an elected advisory body to the naval governor. On December 8, 1941, Imperial Japanese forces invaded Guam, beginning a three-year occupation of the island. The island was eventually retaken in 1944 during the intense Battle of Guam.