The year before the Korean War began the United States established the North Atlantic Treaty Organization in Western and Southern Europe to contain and confront the Soviet Union and its Eastern European allies. NATO opened the door for the Pentagon to maintain, expand and upgrade, and gain access to new, military bases in Europe from Britain to Turkey, Italy to Norway, West Germany to Greece.
During the Korean War and after its end in 1953 (with Greece and Turkey having been absorbed into NATO), the U.S. replicated the NATO model to varying degrees throughout the Asia-Pacific region.
The Australia, New Zealand, United States (ANZUS) Security Treaty was set up in 1951 as troops from all three nations were fighting in Korea. Australian and New Zealand troops would also fight under American command in the Vietnam War under ANZUS obligations.
With U.S. encouragement and support, the next year Britain oversaw the creation of the Middle East Treaty Organization (METO), also known as the Baghdad Pact Organization, which included Iran, Iraq, Turkey and Pakistan. In 1958 the METO/Baghdad Pact supported the U.S.'s deployment of 14,000 troops to Lebanon under the so-called Eisenhower Doctrine.
After the anti-monarchical revolution in Iraq of the preceding year led to that nation leaving the bloc in 1959, METO was renamed the Central Treaty Organization (CENTO): There could be no Baghdad Pact without Baghdad itself where its headquarters had been. (Half a century later the Iraqi capital is home to United States Forces Iraq headquarters.)
All Asia-Pacific SEATO members and partners except for Pakistan - Australia, New Zealand, the Philippines, South Korea, Thailand and South Vietnam - provided the U.S. with troops for the war in Vietnam, but Pakistan withdrew in 1973 because SEATO hadn't supported it in its 1971 war with India. France followed suit in 1975 and SEATO was disbanded two years later, three years after the U.S.-Chinese rapprochement formalized by Richard Nixon and Mao Zedong in Beijing in 1972.
With China the U.S.'s regional and global ally against the Soviet Union, the Southeast Asia Treaty Organization served no further purpose.
ANZUS was weakened in 1984 when a new government in New Zealand forbade all nuclear weapons-capable and nuclear-powered ships from entering its ports. Two years later the Pentagon suspended security guarantees to New Zealand under the ANZUS Treaty, though Australia has maintained its obligations to both the U.S. and New Zealand.
The end of the Cold War and the break-up of the Soviet Union a generation ago eliminated any conceivable rationale for the continuation of Cold War-era military blocs, but instead NATO has expanded from 16 to 28 full members in the interim and has also gained forty new cohorts under several partnership programs. NATO members and partners now account for over a third of the nations in the world.
The North Atlantic bloc, for example, includes Algeria, Egypt, Israel, Jordan, Mauritania, Morocco and Tunisia in its Mediterranean Dialogue program; Bahrain, Kuwait, Oman, Qatar, Saudi Arabia and the United Arab Emirates in its Istanbul Cooperation Initiative; Australia, Japan, New Zealand and South Korea as NATO Contact Countries; and Afghanistan and Pakistan are subsumed under the Alliance-led Tripartite Commission, which met again in Kabul last month. NATO and U.S. troop strength in Afghanistan is now 150,000-strong.
NATO has expanded into former and current territory and integrated past and present members of SEATO, CENTO and ANZUS.
What has also been underway over the past eight years is the consolidation of what is referred to as an Asian NATO which ultimately will include most all members of CENTO, SEATO and ANZUS and dozens of other nations as well.