Short answers, pulled from the story.
The United States launched Campaign Plan Granite II between June and November 1944. This offensive aimed to neutralize Japanese bases in the central Pacific while supporting the Allied drive to retake the Philippines.
Admiral Raymond A. Spruance commanded the Fifth Fleet assembled for this massive undertaking. Vice Admiral Marc Mitscher led Task Force 58 which consisted of fifteen aircraft carriers and seven battleships.
Imperial Japanese Navy's Combined Fleet sortied to attack U.S. Navy forces resulting in heavy and irreplaceable losses to their carrier-borne and land-based aircraft. The resulting defeat crippled Japanese carrier capabilities for the remainder of the war.
Increased radio traffic starting in October 1943 purported a I Alaskan Corps preparing to invade Kurile islands to create confusion. These signals targeted a fictitious IX Amphibious Force and 9th US Fleet to divert attention away from actual invasion targets in the Mariana Islands.
U.S. forces landed on Saipan in June 1944 followed by Guam and Tinian in July 1944. Heavy fighting secured Saipan by July while Guam and Tinian fell in August 1944.