1 United States
The United States is the first country to test a Hydrogen bomb.The first test took place on November 1, 1952 on the small Pacific island of Elugelab at Eniwetok Atoll in the Marshall Islands. The explosion, nicknamed the "Mike Shot", was very successful. The Castle Bravo test was the largest nuclear weapon ever detonated by the United States on 1 March 1954.
On November 22, 1955, Russia had successfully tested the first hydrogen bomb(code name Ivan or Vanya). This weapon had a nominal yield of 1.6 Megaton of TNT. This was the two-stage hydrogen bomb. Tsar Bomba is the most powerful nuclear weapon ever detonated. This bomb was detonated by Russia on 30 October 1961 and had a nominal yield of 50 Megaton of TNT.
3 United Kingdom
In 1957, the United Kingdom began a series of hydrogen bomb tests at Malden Island and Christmas Island, both now part of Kiribati in the central Pacific. Operation Grapple was the codename given to thermonuclear test by the United Kingdom. This bomb had a yield of 300 kilotons of TNT. In 1958, United Kingdom had tested another hydrogen bomb having an explosive yield of about 3 megatons of TNT.