The USA has been a prominent member of the North Atlantic Treaty Organisation (NATO) since it was established in 1949. NATO is the largest and most powerful military alliance in the world.
In theory, the 28-nation organisation is made up of members of equal standing, where each country has one vote in decision-making.
In reality, the USA is the dominant player within NATO. It contributes far more troops, resources and finances than any other single member of the alliance. As a result it is the country most able to set the NATO agenda.
For example, it is claimed the USA has kept the pressure up on European countries to look to expand NATO eastwards.
In recent years, the USA has also tried to encourage the other members of NATO to take a greater responsibility for their own defence and to make a larger contribution to NATO's finances. It has been argued that the US has been focusing its attention more towards Asia and the Far East as opposed to Europe. However, with Russian annexation of the Crimea in 2014, NATO and American support for the Atlantic Alliance has moved close to the top of the US international agenda.
US leadership within NATO remains very important:
However, the US also needs NATO as it allows the US to confront difficult and diverse threats to its security alongside other countries which support democratic values. As part of NATO the US is stronger.