United States Third Fleet The Third Fleet is one of six numbered fleet s in the United States Navy . Third Fleet ' s area of responsibility includes approximately fifty million square miles of the eastern and northern Pacific ocean areas including the Bering Sea , Alaska , the Aleutian Islands and a sector of the Arctic . Major oil and trade sea lines of communication within this area are critically important to the economic health of the United States and friendly nations throughout the Pacific Rim region . History . World War Two . The Third Fleet was originally formed during World War II on 15 March 1943 under the command of Admiral William F . Halsey . Its on - shore headquarters in Pearl Harbor , Hawaii was established on 15 June 1944 . The fleet operated in and around the Solomon Islands , the Philippines , Taiwan , Okinawa and the Ryukyu Islands with the and , from May 1945 to the end of the war , the as its flagship . It also operated in Japanese waters launching attacks on Tokyo , the naval base at Kure and the island of Hokkaidō as well as bombardments of several Japanese coastal cities . The ships of the Third Fleet formed the basis of the Fifth Fleet , which was the designation of the " Big Blue Fleet " when under the command of Admiral Raymond A . Spruance . Spruance and Halsey alternated command of the fleet for major operations , allowing the other admiral and his staff time to plan for subsequent operations . A secondary benefit was confusing the Japanese into thinking that there were actually two separate fleets as the fleet designation flipped back and forth . Embarked aboard his flagship " Missouri " , Admiral Halsey led his fleet into Tokyo Bay on 29 August 1945 . On 2 September , the documents of surrender of the Japanese Empire ending the war were signed on her decks . Third Fleet remained in Japanese waters until late September when its ships were directed to sail for the West Coast of the United States . On 7 October 1945 Third Fleet was designated a reserve fleet and decommissioned from active status . Post - war . On 1 February 1973 , following a reorganization of the Pacific Fleet , the Third Fleet was recommissioned as an active fleet and assumed the duties of the former First Fleet and Pacific Anti - Submarine Warfare Force located at Ford Island , Hawaii . Third Fleet trains naval forces for overseas deployment and evaluates state - of - the - art technology for fleet use . Additionally , Third Fleet could deploy in the event of a major conflict . On 26 November 1986 , Commander , Third Fleet shifted his flag from his headquarters ashore to resume status as an afloat commander for the first time since World War II , aboard . In August 1991 , Third Fleet ’ s commander , his staff and the command ship " Coronado " shifted homeports to San Diego , California . In September 2003 , Commander , Third Fleet shifted his flag from the command ship " Coronado " to headquarters ashore at Point Loma , San Diego , California . USS " Ronald Reagan " and other U . S . Third Fleet ships participated in the International Fleet Review ( IFR ) commemorating the 100th birthday of the Royal Canadian Navy in Victoria , British Columbia . Joining the " Reagan " for the naval review were the cruiser , the destroyer , and the frigate . The naval review took place 9 – 12 June 2010 , and it involved 21 naval ships and more than 8 , 000 naval personnel from Canada , France , Japan , Australia , New Zealand , and the United States . Current operations . The U . S . Third Fleet is assigned a number of missions and responsibilities . Third Fleet ' s primary mission is one of conflict deterrence , but in the event of general war , it would conduct prompt and sustained combat operations at sea to carry out the Pacific Fleet strategy in the theater . Such operations would be executed well forward and early in a conflict to carry out the primary wartime mission of Third Fleet — the defense of the western sea approaches to the United States , including Alaska and the Aleutian Islands . The primary means of carrying out these missions are the five " Nimitz " class aircraft carriers attached to the Third Fleet : In addition , Commander , Third Fleet is designated as a Joint Task Force ( JTF ) commander . In that capacity , the commander and his staff may be assigned responsibilities for command of joint U . S . forces deployed in response to a specific event or contingency . As such , the JTF commander reports via a joint chain of command to a unified commander . Commander , U . S . Pacific Command is the unified commander in the Pacific theater . In peacetime , Third Fleet continually trains Navy and Marine Corps forces for their expeditionary warfare mission . In keeping with the Department of the Navy strategic concept " Forward . . . from the Sea " , these forces provide the flexibility and immediate response necessary to react to any emerging crisis from humanitarian and peacekeeping missions to major regional conflicts . These forces are prepared to provide the critical first response in a transition between peacetime operations and escalating regional tensions . If required , these forces carry the power and capabilities necessary to establish and hold an initial foothold to allow larger joint operations to follow on a large scale in the event a major conflict ensues . Finally , when the conflict is resolved , those naval expeditionary forces remain on the scene to help shape the peace and ensure compliance . Third Fleet training has been designed to ensure that deploying forces are fully prepared for joint operations . All training is conducted within a joint environment — employing joint terminology , doctrine , procedures , command and control — to ensure that forces are ready to join with other branches of the Military under a joint command structure .