The North Atlantic Treaty Organization was formed on April 4th, 1949. A political-military alliance, it was the result of Cold War tensions between the United States and Western Europe on one side and the Soviet Union on the other.

The continued stationing of large amounts of Soviet forces in Eastern Europe made a common defense organization necessary. It was also a way to keep the United States and Canada engaged in the defense of Western Europe from the outset of any conflict, furthering the alliance’s deterrent value.

Article 5 of the NATO charter is the real meat of the alliance agreement. An attack on one member is considered an attack against all. Interestingly, although Article 5 was long associated with a possible Soviet attack on Western Europe, the only time it was invoked was after the September 11th attacks.

The NATO alliance has sought to standardize a variety of military equipment. Ships, aircraft, and armored vehicles are often purchased by multiple NATO member countries. Rifle magazine designs are standardized for interoperability purposes so that a British SA-80 rifle will take magazines from a Norwegian Heckler and Koch 416. Tank main gun ammunition, machine gun ammunition, artillery, and mortar rounds are all standardized. Here are some of the alliance’s most lethal combat systems, each operated by two or more member states.

Source: US Military Technology