overall command structure of the United States military. With the creation of Unified Combatant Commands (UCC) organized either on a geographical basis (known as "Area of Responsibility", AOR) or on a functional basis, Pacific Air Forces became a part of the United States Pacific Command (USPACOM). Andersen AFB in Guam was reassigned from Strategic Air Command (SAC) to PACAF in 1989, and Eleventh Air Force became a part of the command in late 1990. In the late 1980s and early 1990s, civil unrest in the Philippines and negotiations with the extant government of the Republic of the Philippines for the lease of Clark Air Base, along with other U.S. military installations in the Philippines, had reached an impasse. However, following the volcanic eruption of Mount Pinatubo, the resultant damage to Clark AB, and with a post-Cold War desire by the U.S. Government to reduce defense spending, Clark AB was closed and Thirteenth Air Force relocated in 1991. In 1992, changes took place in force structure within PACAF as the command assumed control of theater-based tactical airlift wings, theater C-130 aircraft and crews, and associated theater C-130 support following the disestablishment of Military Airlift Command (MAC). PACAF also gained control of all operational support aircraft and all aeromedical airlift assets in the Pacific previously under the cognizance of MAC. With the concurrent disestablishment of Strategic Air Command (SAC) and Tactical Air Command (TAC) the same year, PACAF also assumed responsibility for all active KC-135 aerial refueling aircraft based in Hawaii and Japan, "gaining command" responsibility for all Air National Guard KC-135 aircraft in Hawaii and Alaska, and all E-3 AWACS aircraft in Japan and Alaska. Throughout its history PACAF has played a vital role in world events. In addition to its key combat role in World War II, Korea and Vietnam, PACAF units fought in Desert Storm in 1991 and continued to deploy to Saudi Arabia, Turkey and Italy for peacekeeping operations such as Operation Southern Watch and Operation Northern Watch. PACAF provided its expertise, aircraft, personnel and equipment to facilitate the new Expeditionary Air Force, especially as it applied to successful airbridge operations spanning the vast Pacific Ocean. Following the 11 September 2001 terrorist attacks on the United States, PACAF again demonstrated its intrepid spirit through its units deployed in support of Operation Noble Eagle, Operation Enduring Freedom and, in 2003, Operation Iraqi Freedom. Since 1944, the command has also