Between 1945 and 1948 Yugoslavia's control over Albania's forces was tighter than Italy's had been. In addition to technical advisers and instructors in regular service units, the Communist Party organization provided an effective vehicle for controlling the reliability of personnel, particularly the military leadership. Because the Soviet Union, like Italy, was physically separated from the country it was a more desirable ally than neighboring Yugoslavia had been. It was nonetheless able to maintain tighter controls over Albanian forces than either Yugoslavia or Italy had achieved. General Petrit Dume, who was commander of the People's Army during its dependence on the Soviet Union and still was in 1970, had said in November of 1952 that his force was an integral part of the Soviet Army. Albania became one of the original Warsaw Treaty Organization members in 1955. Separated from the other signatories, its forces were unable to participate in the pact's field exercises and after 1961, because of its rift with the Soviet Union, was not invited to attend the organization's meetings. In 1968, protesting the Soviet invasion of Czechoslovakia, Albania formally withdrew from the pact. Communist China was Albania's only military ally in 1970. In 1970 the Chinese were believed to be enabling Albania to maintain its forces at approximately the same levels that had been reached by 1960 with Soviet assistance (see ch. 6, Government Structure and Political System). SECURITY FORCES Albanian sources publish little concerning the security police except for some articles expressing gratitude for their services and a smattering of information relative to their responsibilities. Few of the observers who have visited the country since 1945 have been in positions to see, or have been qualified to judge, their actual performance. It is undoubtedly true that the Albanian leadership emulated many of Joseph Stalin's techniques for controlling the population, that it modified its attitudes and practices less than did the other East European Communist countries after Stalin's death, and that it has maintained a high degree of Stalinism since its break with the Soviet Union and alignment with Communist China (see ch. 6, Government Structure and Political System). There is probably credibility in reports stating that no other Communist country has as extensive a police and security organization relative to its size as that which operates in Albania. Hoxha has regarded the security police as an elite group, and they have been the mainstay of his power. By 1961, although arrests had tapered off from earlier levels, fourteen concentration or labor camps were still in use. Foreign visitors in Tirana have reported that it is impossible to move around the city without escorts and that conversations with ordinary citizens are discouraged. Local police, servicemen, and security police are in evidence everywhere.