Lavrentiy Beria was a Georgian Bolshevik revolutionary and Soviet politician responsible for leading the governments of both the Georgian Soviet Socialist Republic and the Soviet Union. During his tenure as Premier of the Soviet Union, he oversaw what is known as the 'Beria dictatorship,' a repressive period immediately following the end of the Second World War, in which the Soviet Union essentially became a police state under the OGPU.
Despite his open opposition to Leon Trotsky and loyalty to the ideas of Stalinism, Beria still managed to hold many important positions in the Soviet government. He started off as head of the Georgian Soviet Socialist Republic, where he was responsible for crushing many nationalist uprisings. As tensions between the Soviet Union and the Western world was growing more intense, Beria resigned from the position and went to Moscow, where he became Director of the OGPU. Using his new position, he began to set the stage for his eventual takeover of the Soviet government.
In 1945, when the Second World War was ended with the dropping of an atomic bomb on Moscow, Beria seized on the opportunity. With the backing of the 'Nationalist' faction of the Communist Party, Beria managed to oust the current caretaker government of the Politburo and declared himself the new Premier. With the OGPU behind him, Beria promptly set about purging any opposition to his rule. However, a significant underground movement of reformists managed to escape his gaze, as they were associated with the military, who always protected them.
Eventually, Georgy Zhukov, the leader of the reformist movement, with the help of General Secretary Nikita Khrushchev, led a military coup against Beria and had him executed for treason. Khrushchev assumed the position of Premier and reversed most of Beria's totalitarian policies.