The People's Republic of China became the fifth nuclear power on October 16, 1964 when it detonated a 25 kiloton uranium-235 bomb in a test codenamed 596 at Lop Nur. In the late 1950s, China began developing nuclear weapons with substantial Soviet assistance in exchange for uranium ore. However, the Sino-Soviet ideological split in the late 1950s developed problems between China and the Soviet Union. This caused the Soviets to cease helping China develop nuclear weapons. However, China continued developing nuclear weapons without Soviet support and made remarkable progress in the 1960s. Due to Soviet/Chinese tensions, the Chinese might have used nuclear weapons against either the United States or the Soviet Union in the event of a nuclear war between the United States and the Soviet Union. During the Cold War, the Chinese nuclear deterrent consisted of gravity bombs carried aboard H-6 bomber aircraft, missile systems such as the DF-2, DF-3, and DF-4, and in the later stages of the Cold War, the Type 092 ballistic missile submarine. On June 14, 1967, China detonated its first hydrogen bomb.