Possessing three Marine Expeditionary Forces (MEFs), the US Marine Corps (USMC) is prepared to defend the United States and its allies anywhere worldwide.

"Within the structure of the MAGTF [Marine Air Ground Task Force], Marines have the will, the determination, and the capability to deploy to battles around the world within six hours," the USMC says on its website.

The MAGTF, which combines a ground combat element, an aviation combat element, a logistics combat element and a command element, is the biggest building block of Marine combat power.

Its size depends on its mission, but its structure never varies.

It can operate either alone or as part of a coalition.

The largest type of MAGTF is a MEF. The USMC has three of them.

Based in Japan, the US West Coast and the US East Coast, I MEF, II MEF and III MEF provide the USMC's foundation for rapid, global response to any crisis.

I MEF

I MEF is based in Camp Pendleton, California.

The largest of the MAGTFs, I MEF "is comprised of approximately 53,000 Marines and Sailors", according to an undated USMC statement.

Its primary components are the 1st Marine Division, 3rd Marine Air Wing and 1st Marine Logistics Group.

While I MEF is intended to primarily support operations in the Indo-Pacific, it maintains the ability to respond to the full-range of crisis response.

Though based in the United States, I MEF has been busy conducting a joint exercise in the Western Pacific in July.

"Approximately 6,000 US Marines ... are dispersed across Australia, the Federated States of Micronesia, Papua New Guinea, the Philippines, and the Republic of Palau," the USMC said of I MEF in a statement.

II MEF

II MEF is headquartered at Camp Lejeune in North Carolina.

It has "more than 47,000 Marines and Sailors", according to the USMC.

"It possesses the capability for projecting offensive combat power ashore while sustaining itself in combat without external assistance for a period of 60 days."

Its component units are the 2nd Marine Division, 2nd Marine Aircraft Wing and 2nd Marine Logistics Group.

II MEF has a broad geographical focus -- Europe, Africa, the Middle East and South America. Since it is not assigned to a specific geographic combatant command, it can deploy wherever force projection is suddenly needed.

The MEF provides a three-star Joint Task Force Headquarters (JTF HQ) and co-ordinate Marine Forces Reserve (MARFORRES) to execute global crisis response operations.

III MEF

III MEF is forward deployed at Camp Courtney in Okinawa, Japan, and focuses on Asia.

"At full strength, III MEF totals nearly 19,000 Marines and Sailors located across 10 camps and an air station on Okinawa," the USMC said in a statement.

Its units include the 3rd Marine Division, 1st Marine Aircraft Wing and 3rd Marine Logistics Group.

III MEF mostly focuses on operations in the First Island Chain -- which arcs southward from the Japanese home islands through the Ryukyu Islands, Taiwan and the Philippine archipelago.

Presently, III MEF units are participating in "multiple training events throughout Japan, the Philippines and Australia", the USMC said in July.

That training helps "to build interoperability between the US Marine Corps and our Allies and partners that contribute to increased readiness of forces, and security and stability in the Indo-Pacific".