In September 1939, Germany invaded Poland, and the country was subsequently occupied by German and Soviet forces. At the outbreak of War, Karol and his father fled eastwards from Kraków with thousands of other Poles. They sometimes found themselves in ditches, taking cover from strafing Luftwaffe aircraft. After walking 120 miles, they learned of the Soviet invasion of Poland and were obliged to return to Kraków. In November, 184 academics of the Jagiellonian University were arrested and the university suppressed. All able-bodied males had to have a job.