The first collective security agreement the United States entered into was the

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The Rio Treaty, signed in 1947, was the first collective security agreement the United States entered into. It established the Organization of American States (OAS) and provided for mutual defense among the nations of the Americas. The North Atlantic Treaty (NATO) was not signed until 1949, the Southeast Asia Treaty Organization (SEATO) was formed in 1954, and the Australia, New Zealand, United States Security Treaty (ANZUS) was signed in 1951.

The First Collective Security Agreement the United States Entered into Was