Quoc: On 29 August 1949, the Soviet Union secretly conducted its first successful weapon test (First Lightning), based on the U.S. design at the Semipalatinsk in Kazakhstan.

When did the soviets explode first atomic bomb?
HW Chung: OK, some thoughts:
The relevant information to answer the above question is: On 29 August 1949, the Soviet Union secretly conducted its first successful weapon test (First Lightning), based on the U.S. design at the Semipalatinsk in Kazakhstan. The answer is On 29 August 1949.