Explanation: Nikita Khrushchev (not an actual pic of him here, but a frame from the movie The Death of Stalin, where he is played by Steve Buscemi) was the reformist premier of the Soviet Union in the 1950s. When workers rose up and attempted to implement a democratic socialist regime in Hungary, the upper echelons of the Soviet Union were in disagreement over what to do next. Some, like the WW2 hero Field Marshal Zhukov, suggested simply letting the Hungarians find their own way. Many hardliners demanded military action to 'punish' and bring the Hungarians back into the Soviet fold by force.
Despite some hesitation, Khrushchev eventually acquiesced to the hardliner position out of fear of seeming 'weak' and losing his grip on power in domestic Soviet politicking. From this incident, wherein the Soviet Union invaded Hungary, crushing the workers' militias with professional military forces, including tanks, we get the term 'tankie'.