He grew increasingly concerned that senior political and military figures might try to oust him; he prevented any of them from becoming powerful enough to rival him and had their apartments bugged with listening devices. He demoted Molotov, and increasingly favoured Beria and Malenkov for key positions. In 1949, he brought Nikita Khrushchev from Ukraine to Moscow, appointing him a Central Committee secretary and the head of the city's party branch. In the Leningrad Affair, the city's leadership was purged amid accusations of treachery; executions of many of the accused took place in 1950.