Simić was in touch with General Dušan Simović, with whom he met on 26 March, the day before the Yugoslav coup d'état took place, and informed him about the Soviet Union's mood to conclude an agreement with Yugoslavia. In the Government of Dušan Simović, he was appointed minister without portfolio. As a minister without portfolio, he and Dušan Simović participated in negotiations with Stalin, and immediately after the military "coup d'état" on 27 March 1941, Mustafa Golubić, the senior NKVD officer and Božin Simić travelled together from Belgrade to Moscow to attend the signing of the Yugoslav-Soviet Union Friendship Agreement. German forces invaded the country ten days later.