An acronym for the North Atlantic Treaty Organization. A military alliance formed by North American and European countries, with the United States playing a central role. It was established after World War II to counteract the threat posed by the Soviet Union and other Communist states. It officially came into being in 1949 with the signing of the North Atlantic Treaty. NATO allies were commonly referred to as the "Western Bloc," while Communist countries were called the "Eastern Bloc." The original member states of 1949 were the United States, Canada, the United Kingdom, France, the Netherlands, Belgium, Luxembourg, Iceland, Norway, Denmark, Italy, and Portugal. Following the end of the Cold War, the NATO-Russia Council was established in 2002. In 2004, the former Eastern Bloc countries of Bulgaria, Estonia, Latvia, Lithuania, Romania, Slovakia, and Slovenia joined the alliance, bringing the total number of member countries to 26.