@legendary.sukhoi: RDS-37 (Russian: РДС-37) was the Soviet Union's first two-stage hydrogen bomb, first tested on 22 November 1955. The weapon had a nominal yield of approximately 3 megatons. It was scaled down to 1.6 megatons for the live test.[1] RDS-37 RDS-37 in testing (1955) Information Country Soviet Union Test site Semipalatinsk Test Site, Kazakh SSR Period November 1955 Number of tests 1 Test type Atmospheric test Device type Fusion Max. yield Total yield 1.6 megatons of TNT (6.7 PJ)