1949 the ussr atomic bomb caused the nuclear clock to move to 3 minutes to midnight. 1953 united states decides to pursue the hydrogen bomb, a weapon far more powerful than any atomic bomb. In october 1952, the united states tests its first thermonuclear device, obliterating a pacific ocean islet in the process; nine months later, the soviets test an h-bomb of their own, clock strikes 5 to midnight. 1963 after a decade of almost non-stop nuclear tests, the united states and soviet. Union sign the partial test ban treaty, which ends all atmospheric nuclear testing. While it does not outlaw underground testing, the treaty represents progress in at least slowing the arms race. It also signals awareness among the soviets and united states that they need to work together to prevent nuclear annihilation better management 12 mins to midnight. 1968 7 mins because new players in nuclear war china and france.