In March 1945, a staged trial of 16 leaders of the Polish Underground State held by the Soviet Union took place in Moscow - (Trial of the Sixteen). The Government Delegate, together with most members of the Council of National Unity and the C-i-C of the Armia Krajowa, were invited by Soviet general Ivan Serov with agreement of Joseph Stalin to a conference on their eventual entry to the Soviet-backed Provisional Government. They were presented with a warrant of safety, yet they were arrested in Pruszków by the NKVD on 27 and 28 March. Leopold Okulicki, Jan Stanisław Jankowski and Kazimierz Pużak were arrested on 27th with 12 more the next day. A. Zwierzynski had been arrested earlier. They were brought to Moscow for interrogation in the Lubyanka. After several months of brutal interrogation and torture, they were presented with the forged accusations of "collaboration with Nazi Germany" and "planning a military alliance with Nazi Germany".