In 1949, America and eleven other nations sign the North Atlantic Treaty, creating NATO, a military alliance with the purpose of countering the Soviet Union and its allies.

The North Atlantic Treaty, signed in Washington, D.C. on 4 April 1949, is the treatyestablishing the North Atlantic Treaty Organization (NATO).

Background
The treaty was drafted by a committee in talks in Washington which was chaired byTheodore Achilles. Earlier secret talks had been held at the Pentagon between 22 March and 1 April 1948, of which Achilles said:

The talks lasted about two weeks and by the time they finished, it had been secretly agreed that there would be a treaty, and I had a draft of one in the bottom drawer of my safe. It was never shown to anyone except Jack. I wish I had kept it, but when I left the Department in 1950, I dutifully left it in the safe and I have never been able to trace it in the archives. It drew heavily on the Rio Treaty, and a bit of the Brussels Treaty, which had not yet been signed, but of which we were being kept heavily supplied with drafts. The eventual North Atlantic Treaty had the general form, and a good bit of the language of my first draft, but with a number of important differences.[1]

According to Achilles, another important author of the treaty was John D. Hickerson:

More than any human being Jack was responsible for the nature, content, and form of the Treaty...It was a one-man Hickerson treaty.[2]

The treaty was created with an armed attack by the Soviet Union against Western Europe in mind, but the mutual self-defense clause was never invoked during the Cold War. Rather, it was invoked for the first time in 2001 in response to the 11 September 2001 attacks against the World Trade Center and The Pentagon in Operation Eagle Assist.