In terms of combat, 1943 was a relatively quiet year, but it proved decisive inasmuch as Nimitz gained the materiel and manpower needed to launch major fleet offensives to destroy Japanese power in the central Pacific region. This drive opened with the Gilbert and Marshall Islands campaign from November 1943 to February 1944, followed by the destruction of the strategic Japanese base at Truk Lagoon, and the Marianas campaign that brought the Japanese homeland within range of new strategic bombers. Nimitz's forces inflicted a decisive defeat on the Japanese fleet in the Battle of the Philippine Sea (June 19–20, 1944), which allowed the capture of Saipan, Guam, and Tinian. His Fleet Forces isolated enemy-held bastions on the central and eastern Caroline Islands and secured in quick succession Peleliu, Angaur, and Ulithi. In the Philippines, his ships destroyed much of the remaining Japanese naval power at the Battle of Leyte Gulf, October 24 to 26, 1944. With the loss of the Philippines, Japan's energy supply routes from Indonesia came under direct threat, crippling their war effort.