Main Operating Base is a term used by the United States military defined as "an overseas, permanently manned, well protected base

Military base

A military base is a facility directly owned and operated by or for the military or one of its branches that shelters military equipment and personnel, and facilitates training and operations. In general, a military base provides accommodations for one or more units, but it may also be used as a...

, used to support permanently deployed forces, and with robust sea and/or air access." This term was used to differentiate major strategic overseas military facilities versus smaller, less-secure or temporarily-manned contingency tactical locations such as Forward Operating Base

Forward Operating Base

A forward operating base is any secured forward military position, commonly a military base, that is used to support tactical operations. A FOB may or may not contain an airfield, hospital, or other facilities. The base may be used for an extended period of time. FOBs are traditionally supported...

s, Forward Operating Site

Forward Operating Site

A Forward Operating Site or Forward Operating Location is a U.S. military term for facilities, defined as "a scalable, 'warm' facility that can support sustained operations, but with only a small permanent presence of support or contractor personnel...

s or Cooperative Security Location

Cooperative Security Location

A Cooperative Security Location is a U.S. military term for facilities used for regional training in counterterrorism and interdiction of drug trafficking, and also to provide contingency access to the continent. "A CSL is a host-nation facility with little or no permanent U.S...

s. The differentiation was established as the Pentagon

The Pentagon

The Pentagon is the headquarters of the United States Department of Defense, located in Arlington County, Virginia. As a symbol of the U.S. military, "the Pentagon" is often used metonymically to refer to the Department of Defense rather than the building itself.Designed by the American architect...

 began to address regional threats primarily in Africa

Africa

Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

, Asia

Asia

Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

 and Latin America

Latin America

Latin America is a region of the Americas where Romance languages  – particularly Spanish and Portuguese, and variably French – are primarily spoken. Latin America has an area of approximately 21,069,500 km² , almost 3.9% of the Earth's surface or 14.1% of its land surface area...

 following its 2004 global posture review.