Simplify the following text for a Grade 7 native English-speaking person.
Original: Moreover , expecting to succeed Joseph Stalin as leader of the USSR , the ambitious head of the MVD ( Ministry of Internal Affairs ) , Lavrentiy Beria merged the MGB and the MVD on Stalin 's death in 1953 .
Simplified: In March 1953 , Lavrenty Beria merged the MVD and the MGB into one agency -- the MVD .