On December 29, 1945 Kruglov replaced Lavrentiy Beria as the People's Commissar of Internal Affairs of the Soviet Union (head of NKVD). In 1946 the Soviet government transitioned to the ministerial system and the security apparatus underwent substantial reorganization. NKVD became the Soviet Ministry of Internal Affairs (MVD), with Kruglov as its chief, the Minister of Internal Affairs. NKGB became the Soviet Ministry of State Security (MGB), and it was headed by Viktor Abakumov, who replaced Beria's protégé Vsevolod Merkulov. Beria became Deputy Prime Minister and retained overall nominal control over both MVD and MGB, which were both, however, now led by Beria's adversaries.