President Harry S Truman and Secretary of State Dean Acheson at the ceremony marking U.S. joining the N.A.T.O. alliance in 1949

---

1947: Inter-American Treaty of Reciprocal Assistance (Rio Treaty).

1949: North Atlantic Treaty Organization (N.A.T.O.).

1951: Greece and Turkey formally are added to N.A.T.O.
 
1951: US-Japanese Treaty

1951: ANZUS Treaty ties US to the defense of Australia and New Zealand

1952: Mutual Security Act: military aid to 8 Rio Treaty signatories

1952: Base agreements signed with Morocco, Libya and Saudi Arabia

1953: Base Agreements signed with Spain

1954: Southeast Asia Treaty Organization (S.E.A.T.O.) links the US to Pakistan, France, Britain, Thailand, Philippines, Australia, and eventually, South Vietnam

1955: Indirect tie established to Iran and Iraq, in the "Baghdad Pact,"  to which Britain was a signatory but the U.S. was not

---

A more thorough collection of treaties from this era, along with their full texts, is available online at the Avalon Project, Yale University School of Law.