On 11–14 September 1939, during the invasion of Poland, which started World War II, the German and Polish armies fought the Battle of Przemyśl in and around the city. Afterwards the battle German "Einsatzgruppe I" entered the city to commit various atrocities against the population, and the "Einsatzgruppe zbV" entered to take over the Polish industry. The battle was followed by three days of massacres carried out by the German soldiers, police and "Einsatzgruppe I" against hundreds of Jews who lived in the city. In total, over 500 Jews were murdered in and around the city and the vast majority of the city's Jewish population was deported across the San River into the portion of Poland that was occupied by the Soviet Union. The border between the two invaders ran through the middle of the city along the San River until June 1941. German-occupied left-bank Przemyśl was part of the Kraków District of the General Government. Members of the "Einsatzgruppe I" co-formed the local German police unit. On November 10, 1939, the Germans carried out mass arrests of Poles in left-bank Przemyśl and the county, as part of the "Intelligenzaktion". Arrested Poles were detained in the local German police prison, and then deported to a prison in Kraków, from where they were eventually deported to the Auschwitz concentration camp. The Soviet-occupied right-bank part of the city was incorporated to the Ukrainian SSR in the atmosphere of NKVD terror as thousands of Jews were ordered to be deported. It became part of the newly established Drohobych Oblast. In 1940, the city became an administrative center of Peremyshl Uyezd with the Peremyshl Fortified District established along the Nazi-Soviet frontier before the German attack against the USSR in 1941.