A Polish engineer named Gwidon Damazyn, who had been a prisoner since March 1941, had set up a secret short-wave radio. On April 8 at noon, Damazyn and Russian prisoner Konstantin Ivanovich Leonov sent a message in Morse code to the Allies. The message had been written by the leaders of the prisoners' underground resistance movement (a group of prisoners who tried to fight the Nazis in secret). It said: