Earlier in his career, Andropov served as the Soviet ambassador to Hungary from 1954 to 1957, during which time he was involved in the suppression of the 1956 Hungarian Uprising. He was named Chairman of the KGB on 10 May 1967. In this position, he oversaw a massive crackdown on dissent carried out via mass arrests and the involuntary psychiatric commitment of people deemed "socially undesirable". After Brezhnev suffered a stroke in 1975 impairing his ability to govern, Andropov effectively dictated Soviet policymaking alongside Foreign Minister Andrei Gromyko and Defense Ministers Andrei Grechko (1967—1976) and Dmitry Ustinov (1976—1983) for the rest of Brezhnev's rule.