in Poland, those who remained politically active and in favor ruled the country, aided by the MBP and Soviet "advisers", who were placed in every arm of the government and state security as a guarantee of pro-Soviet policy of the state. The most important of them was Konstantin Rokossovsky (Konstanty Rokossowski in Polish), defense minister of Poland from 1949 to 1956, Marshal of the Soviet Union and war hero. Military conscription was introduced following a postwar hiatus and the army soon reached its permanent size of 400,000 men. The Soviet-style secret police including the Department of Security (UB) grew to around 32,000 agents as of 1953. At its Stalinist peak, there was one UB agent for every 800 Polish citizens. The MBP was also in charge of the Internal Security Corps, the Civil Militia (MO), border guard, prison staff and paramilitary police ORMO used for special actions (with over 100,000 members). The ORMO originated from popular self-defense efforts, which were a spontaneous reaction to the explosion of crime in the power vacuum of 1944–45. In February 1946, the PPR channeled and formalized this citizen militia movement, creating its ostensibly crime control voluntary ORMO structure. Primarily in Stalin's lifetime, public prosecutors and judges as well as functionaries of the Ministry of Public Security and the Main Directorate of Information of the Polish Army engaged in acts recognized by international law as crimes against humanity and crimes against peace. One example was the 1951 Mokotów Prison execution in Warsaw of members of the Freedom and Independence (WiN) organization, former participants in anti-Nazi resistance, after the official amnesty and their voluntary disclosure. The postwar Polish Army, intelligence and police were staffed with Soviet NKVD officers who stationed in Poland with the Northern Group of Forces until 1956. Mass arrests continued during the early 1950s. In October 1950, 5,000 people were arrested in one night in the so-called "Operation K". In 1952, over 21,000 people were arrested. By the second half of 1952, according to official data, 49,500 political prisoners were being held. Former Home Army commander Emil August Fieldorf was subjected to several years of brutal persecution in the Soviet Union and Poland before being executed in February 1953, just before Stalin's death. Resistance to the Soviet and native Stalinists was widespread among not only the general population but also the PZPR ranks, which limited the oppressive system's damage in Poland to well