A mutual defense pact is an international agreement obligating the nations which sign to come to each other’s defense – under specific circumstances outlined in the treaty.

Currently, the United States is involved with seven mutual defense pacts, tying the nation’s fate (and military) to a number of others.

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1947 – Inter-American Treaty of Mutual Assistance (Rio Treaty)

Also known as the “Rio Treaty,” this 1947 agreement includes a total of 18 nations, the newest being the Bahamas which became a signatory in 1982. The pact stipulates that an attack against any of these nations, specific to the American hemisphere, is an attack against them all.

Mexico withdrew from the treaty in 2002 following the September 11 attacks (when the pact was first activated, according to the UN Terminology database), calling it obsolete and unnecessary. A decade later Bolivia, Nicaragua, Venezuela, and Ecuador retired as well.

1949 – North Atlantic Treaty Organization (NATO)

NATO is based on the North Atlantic Treaty, an international government military alliance signed by 28 nations, agreeing to mutual defense in response to any attack by outside parties.

Since it was formed in 1949, NATO’s article five, which states that an attack against one nation is an attack against all, has only been invoked only once – after the September 11, 2001 attacks – resulting in NATO counter-terrorist missions.

Article 6 – which calls not for action, but military consultation, has been invoked three times by Turkey.

1951, 1953, 1954 (Separate) Mutual Defense Treaties with the Philippines, South Korea, and Japan

In the early ‘50s, the United States signed three separate mutual defense treaties with the Philippines, South Korea, and Japan, recognizing armed attacks against one party a threat to the other, and take action to meet that common danger.

These treaties all still stand, and are proving controversial due to several potential East Asian flashpoints – China and Japan’s dispute over the Sankaku/Diaoyu islands in the East China Sea, China and the Philippines’ dispute over Spratlys islands in the South China Sea, and South Korea’s provocative nuclear capabilities.

The United States’ historical commitments to these nations mean that our military is deeply involved in each, and would be required take action if the disputes turned hostile – an involvement that, in the opinion of Forbes, is not only one-sided, but serves only to increase the nations’ instability and insecurity.

Other current and dissolved U.S. defense treaties

The U.S. has been involved several other treaties over the years, three of which have since been terminated or dissolved, lasting only slightly over 20 years each.

These include SEATO, the 1954 South East Asia Treaty Organization (dissolved in 1977), the 1954 Sino-American Mutual Defense Treaty with the Republic of China (terminated by the U.S. in 1980), and 1955’s CENTO, an alliance with the UK and Middle East (dissolved in 1979.)

Other US Defense Treaties that still stand include 1951’s ANZUS, the mutual defense treaty between the U.S., New Zealand, and Australia, and the 1962 Nassau agreement, between the U.S. and the U.K.