State Protection Authority

The State Protection Authority (Hungarian: Államvédelmi Hatóság or ÁVH) was the secret police force of Hungary from 1945 until 1956. It was conceived of as an external appendage of the Soviet Union's secret police forces, but attained an indigenous reputation for brutality during a series of purges beginning in 1948, intensifying in 1949 and ending in 1953. In 1953 Joseph Stalin died, and Imre Nagy (a moderate reformer) was appointed Prime Minister of Hungary. Under Nagy's first government from 1953 to 1955, the ÁVH was gradually reined in.

More information on the English and Hungarian  Wikipedia pages.