Barys Rahula was born near Navahrudak and spent his early years in West Belarus, then part of the Second Polish Republic. In 1938, he became student at the University of Vilnius but was mobilized into the Polish army after the Nazi-Soviet invasion of Poland. He soon became a German POW, but in 1940 escaped from German prison to West Belarus occupied by the Soviets. In Belarus, he got arrested by the NKVD but managed to escape from prison in the first days after Germany's attack on the USSR.