Balashevo

The Balashevo (БАЛАШЕВО Rus.) is the Soviet ship that was docked in Tokyo Bay in The Return of Godzilla. The ship contained onboard controls for a Soviet satellite armed with nuclear missiles. While Godzilla was being attacked by the military in the bay, he submerged himself. The resulting wake knocked the Balashevo into the harbor and disrupted some of it's systems, the most crucially of which were the controls of the armed satellite. This triggered a countdown to fire a nuclear missile at Tokyo. The Kashirin, who under government orders had earlier disabled the firing system, attempted to shut down the launch sequence. After squeezing through the broken doorway, the captain was killed in a small explosion before being able to stop the countdown. Eventually a nuclear missile was fired at Tokyo as a result.

U.S. Version
Because of Cold War tensions between the US and the Soviets at the time this movie was made (and edited for American audiences), the US version edits the film so that the Soviets are the sole aggressors. This is in contrast to the original Japanese version in which the US and the Soviets are basically on the same level, both trying to use the Godzilla situation to their advantage. The American version edits the film so that the captain of the Balashevo sets the nuclear missile to launch rather than trying to disable it.