During the invasion of Poland by Germany in 1939, Korczak fled to Lituania and met Vitka Kempner in Vilna thanks to HaShomer HaTzair.[3] Upon Germany's invasion of the Soviet Union, she co-founded the United Partisan Organization (FPO) with Abba Kovner and Kempner in 1942.[4] They smuggled weapons into the Vilna Ghetto and smuggled Jews out.[3]