Following the Moscow Declaration on German Atrocities in Occupied Europe of October 1943, the Allies agreed in Potsdam in August 1945 that “war criminals and those who have participated in planning or carrying out Nazi enterprises involving or resulting in atrocities or war crimes shall be arrested and brought to judgment. Nazi leaders, influential Nazi supporters, and high officials of Nazi organizations and institutions, and any other persons dangerous to the occupation or its objectives shall be arrested and interned.” During the immediate postwar years, the internment practices by the Allies of the anti-Hitler coalition were quite similar. Altogether, the Allies interned about four hundred thousand people who were suspected of constituting a danger to occupation policies (a “security threat”) or who had held a rank in the Nazi state apparatus (categorized for “automatic arrest”). In every Allied occupation zone in Germany, investigation of personal guilt and prosecution of “Nazi and war crimes” was not a prerequisite for internment, which can be seen foremost as a means of Allied security policy immediately after the end of the war, in a situation that was still militarily unsafe for the occupying powers. But how was internment connected to the Allies’ overall goal, formulated in the Moscow and Potsdam declarations, to determine and prosecute individual guilt—especially if the crimes affected their own citizens? This chapter will trace the identification and prosecution of guilty parties in the context of internment and Soviet occupation policy by examining the Soviet investigations in the context of internment, the practices of extradition between the Allied forces, and the convictions of former internees in Soviet military tribunals (SMTs), which were held mostly in secret. In connection with our analysis of these procedures, we seek to answer how the secrecy of both internment and prosecution affected the perception and assessment of Soviet efforts to prosecute war crimes in German society. We make extensive use of material from the Russian state archive of the Department of Soviet Special Camps in Germany, an element of the Soviet People’s Commissariat of Internal Affairs (NKVD; renamed Ministry of Internal Affairs, or MVD, in mid-1946). This collection, however, does not contain individual camp prisoner records or case files. The Soviet material is complemented with sources from German and British archives.