U.S. Pacific Command (PACOM), America's largest and oldest unified combatant command, turned 70 on Jan. 1, 2017.

Since 1947, PACOM sailors, soldiers, Marines, airmen and Coast Guardsmen have stood watch across half the planet, from Hollywood to Bollywood to the Arctic and Antarctic. The combatant command, or COCOM, is responsible for military operations in an area of more than 100 million square miles, or roughly 52 percent of the Earth's surface.

Today, PACOM protects and defends the territory of the United States, its people and its interests through security cooperation with allies and partners, responding to contingencies, deterring aggression, and, if necessary, fighting to win.

PACOM has a complex and storied history that can trace its roots back to World War II, when separate commands were created to command and control U.S. military forces in the Pacific theater.

Its evolution from a string of separate command structures to a unified combatant command begins in 1942.

ORIGINS

In 1942, the roots of PACOM were two separate commands that divided the military forces in the Pacific between the Southwest Pacific Area, under the command of General Douglas MacArthur, and the Pacific Ocean Areas, under Admiral Chester W. Nimitz.

During WWII, the nature and mission of the Army and Navy were too different to establish a unified command structure for all troops in the Pacific theater. The two commands continued after the war ended in 1945, with Fleet Admiral Nimitz as the Commander in Chief of Pacific Fleet and Pacific Ocean Area and General of the Army MacArthur as Commander in Chief of U.S. Army Forces Pacific.

UNIFIED COMMAND PLAN

Before the Unified Command Plan, President Harry S. Truman signed and approved the Outline Command Plan that established seven unified combatant commands, the first ones being sprouted in the Pacific.

The Far East Command (FECOM), Pacific Command, and Alaskan Command were established by a Joint Chiefs of Staff directive in December 1946 with varying degree of responsibilities, areas of operations and missions.

PACOM shared its original headquarters with the Pacific Fleet at Makalapa, Pearl Harbor, in the Territory of Hawaii.

1950s

After a revision of the Unified Command Plan in February, 1950, PACOM assumed responsibility for South Korea, then the Western approaches to the Panama Canal. By 1951, PACOM's geographic area of responsibility would stretch from the West Coast of America to Burma and the Indian Ocean.

The Korean War was the young PACOM's first test of its unified command structure for U.S. military forces in the Pacific. FECOM focused on combat operations during the Korean War. It was then that PACOM was transferred FECOM's responsibilities in the Mariana, Bonin, and Volcano Islands. A year later, PACOM was assigned responsibility for the Philippines, the Pescadores and Formosa (Taiwan).

Significant changes in how the Pacific theater would be managed came with the new Unified Command Plan (UCP) in June of 1956. Major changes from 1956 to 1957 meant that PACOM would inherit more responsibility within the region: the disestablishment of FECOM; the duty for protection of sea communications in Alaskan waters; the establishment of two subordinate unified commands, U.S. Forces Japan and U.S. Forces Korea.

The new UCP also added service components for the Air Force and the Army; U.S. Army Pacific and U.S. Air Forces Pacific were subsequently assigned to PACOM.

In 1957, PACOM moved its headquarters from Makalapa to Camp H.M. Smith, where it still exists today.

1960-1980

In 1971, during the Vietnam War, a new UCP was approved and PACOM assumed responsibility for the Indian Asian and countries of Southern Asia. The Aleutian Islands and parts of the Arctic Ocean were taken off Alaska Command's plate (until it was disestablished in 1975). The COCOM's reach extended westward to the eastern border of Iran until 1976, when its boundaries changed again.

When PACOM took responsibility over the entire Indian Ocean and east coast of Africa, its area of responsibility spread across more than 100 million square miles.

1980s

With U.S. national focus shifting towards the Middle East, the newly formed U.S. Central Command relieved responsibilities for Afghanistan and Pakistan from PACOM in 1983.

The relief was brief, since the same Unified Command Plan of 1983 included new responsibility over China, North Korea, Madagascar, Mongolia, and Alaska.

In 1989, a different version of Alaska Command was established to be a subordinate command to PACOM.

TURN OF THE CENTURY

The new millennium brought more responsibilities to the newly established PACOM. In 2002, Antarctica was added to its list, as well as support to U.S. European Command in the Russian Far East. More areas were reassigned to CENTCOM and U.S. Northern Command, including the Seychelles archipelago, Alaska, the U.S. West Coast, and the Aleutian Islands.

The newly established U.S. Africa Command in 2008 transferred all areas of the Indian Ocean previously assigned to PACOM west of 68 degrees east to the youngest COCOM.

Alaska Command was transferred to NORTHCOM in 2014 in order to streamline the command and control of forces in Alaska.

In 2002, Secretary of Defense Donald Rumsfeld declared that the title "Commander in Chief" should refer only to the President of the United States. Effective on October 24, 2002, all combatant commanders removed "in Chief" from their titles; "USCINCPAC" was redesignated "Commander, U.S. Pacific Command."

Today, PACOM is an engaged and trusted ally and partner, committed to preserving the security, stability, and freedom necessary for enduring regional prosperity. Its history has proven that the Pacific remains one of the most dynamic, ever-shifting security environments in the world.