III Marine Expeditionary Force III Marine Expeditionary Force ( III MEF ) is a formation of the Marine Air - Ground Task Force of the United States Marine Corps . It is forward - deployed and able to deploy rapidly conduct operations across the spectrum from humanitarian assistance and disaster relief to amphibious assault and high - intensity combat . It maintains a forward presence in Japan and Asia to support the Treaty of Mutual Cooperation and Security between the United States and Japan ( 1960 ) and other alliance relationships of the United States . III MEF also conducts combined operations and training throughout the region in support of the National Security Strategy for Theater Security Cooperation . The Marines and sailors of III MEF engage in more than 65 combined , bilateral and multi - lateral training exercises annually throughout the Asia - Pacific region , in countries including treaty allies Japan , the Kingdom of Thailand , the Republic of Korea , the Republic of the Philippines , and Australia . These exercises build partner capacity , develop and maintain strong regional alliances and military - to - military contacts . These exercises prepare III MEF to conduct operations ranging from major combat operations to humanitarian assistance and disaster relief ( HA / DR ) . III MEF has played a significant role in humanitarian assistance and disaster relief missions throughout the region . The MEF assisted the relief efforts led by the Government of Japan during Operation Tomodachi after an earthquake and tsunami struck Honshu March 11 , 2011 . III MEF also conducted HA / DR missions in Thailand in Oct . 2011 , the Republic of the Philippines in Oct . 2010 , and Indonesia in Oct . 2009 . Mission . Commanded by a lieutenant general with its headquarters at Camp Courtney , III MEF ' s mission is to provide forward based and deployed forces to the commander , U . S . Pacific Command , to conduct Phase 0 engagement and theater secutiry cooperation events , support contingencies and emergent requirements , and prepare to rapidly execute existing operations plans in support of the theater and national military strategies . III MEF is organized as a Marine Air Ground Task Force ( MAGTF ) to provide a rapidly deployable , flexible self - contained fighting force . The Marines combine air , ground , and logistics forces to operate as a coherent , self - sufficient force . Each mission dictates the MAGTF ' s scale and structure , giving the Marine Corps the flexibility to respond to any crisis and making a " force in readiness . " A MEF is the largest of all MAGTFs . History . III Marine Expeditionary Foce was activated as I Amphibious Corps Oct . 1 , 1942 in Camp Elliott , San Diego , Calif . Later that month , they were deployed to Noumea , New Caledonia . The unit was redesignated as III Amphibious Corps April 15 , 1944 . III Amphibious Corps was deactivated June 10 , 1946 . III Marine Expeditionary Force was activated May 6 , 1965 at Da Nang , Republic of Vietnam . III MEF was redisgnated to III Marine Amphibious Force ( III MAF ) May 7 , 1965 . III Marine Amphibious Force deployed to Camp Courtney , Okinawa April 1971 . III MAF was redesignated to III Marine Expeditionary Force Feb . 5 , 1988 . World War II . During World War II , III MEF was known as I Marine Amphibious Corps was renamed III Amphibious Corps on April 15 , 1944 , and took part in fighting against the Japanese Empire in the Pacific theater during World War II . It fought in some of the bloodiest battles , including the Solomon Islands Campaign , the Mariana and Palau Islands campaign and the Battle of Okinawa . III Amphibious Corps redeployed to Tientsin , China in Sept . of 1945 where it participated in the occupation of Northern China until June 1946 . III Amphibious Corps was deactivated June 10 , 1946 . Vietnam War . III MEF was reactivated May 6 , 1965 in Da Nang , Republic of Vietnam . May 7 , 1965 , III MEF was redisgnated as III Marine Amphibious Force ( III MAF ) and consisted of the 1st Marine Division , 3rd Marine Division and the 1st Marine Aircraft Wing . The III MAF ' s area of operations was in the northern I Corps Tactical Zone . III MAF participated in the Vietnam War from May 1965 - April 1971 operating from Quang Tri , Thua Thien , Quang Nam , Quang Tin , and Quang Ngai . III MAF deployed to Camp Courtney , Okinawa in April 1971 . Humanitarian Assistance and Disaster Relief . One of the biggest roles III MEF plays in the Asia - Pacifc region is humanitarian assistance and disaster relief ( HA / DR ) . III MEF elements participated in Operation Unified Assistance in response to the tsunami disaster in Southeast Asia from Dec . 2004 - Feb . 2005 . III MEF has also assisted with the Pakistan earthquake response from Oct . 2005 - March 2006 ; Philippine mudslide response in March and April 2006 ; Indonesia earthquake response in May and June 2006 ; Legazpi typhoon recovery in March 2007 ; Solomon Islands tsunami response in April 2007 ; Operation Sea Angel II in Bangladesh from Nov . - Dec . 2007 ; Operation Caring Response in Burma from May – June 2008 ; Taiwan typhoon relief in Aug . 2009 ; Philippine typhoon and Indonesian earthquake relief in Oct . 2009 ; Philippine typhoon relief in Oct . 2010 ; Operation Tomodachi in May 2011 ; Thailand flood relief from Oct . - Nov . 2011 ; and Philippine typhoon relief in Dec . 2012 . Other Significant Events . Since III MAF was redesignated to III Marine Expeditionary Force ( III MEF ) February 5 , 1988 , they have participated in many different operations . These operations include Operation Desert Shield , Operation Desert Storm and Operation Provide Comfort in Southwest Asia and Iraq from Sept . 1990 - April 1991 and May – June 1991 . III MEF elements have also played a vital role in Operation Sea Angel in Bangladesh from May – June 1991 ; Operation Fiery Vigil in The Philippines June 1991 ; Operation Restore Hope and Operation Continue Hope in Somalia from Dec . 1992 - March 1994 . III MEF elements have also had a significant impact on Operation Iraqi Freedom and Enduring Freedom . Structure . The III MEF is part of Marine Forces , Pacific .