Further units were led by SD agents Lothar Schollhorn and Winifred Oberg, but they did not suspect the Soviets knew about them because of Meyer. Stalin offered to let Roosevelt and Churchill stay in the Soviet embassy during the conference. However, Roosevelt insisted on staying at the US embassy on the other side of the city, but the planned ambush of the Big Three was disrupted because the British arrested Holten-Pflug and his group on the night of 31 November.