A month after Britain's first atomic weapons test, America tested the first thermonuclear (hydrogen) bomb. The Soviets responded with Joe 4, a boosted fission weapon, in 1953. Penney believed that Britain could not afford to develop a hydrogen bomb. Henry Tizard believed that the nation should focus on conventional forces instead of duplicating the nuclear capabilities of the American forces that were already defending Britain and Europe: "We are a great nation, but if we continue to behave like a Great Power we shall soon cease to be a great nation. Let us take warning from the fate of the Great Powers of the past and not burst ourselves with pride."