Final answer:
The Treaty of Alliance and Mutual Assistance signed in Dunkirk in 1947 was retitled as NATO in 1949 when the United States, Canada, and five additional European countries joined.
Step-by-step explanation:
In 1949, the Treaty of Alliance and Mutual Assistance, also known as the Dunkirk Treaty, was retitled as the North Atlantic Treaty Organization (NATO). The United States, Canada, and five additional European countries joined the original signatories, France and the United Kingdom, to form NATO. This treaty was created to provide military assistance and mutual defense against potential Soviet aggression.