Szare Szeregi
After the German invasion of Poland in September 1939, Bytnar lived in occupied Warsaw and worked as a glazier and school tutor. In October 1939, together with a group of friends, he joined the short lived left wing Polish People's Independent Action ("Polska Ludowa Akcja Niepodległościowa", PLAN), a resistance group. As its member he composed and distributed pamphlets in response to the formation of the General Government by the Nazis. However, the organization was soon infiltrated by the Gestapo and broken up by January 1940. Bytnar left Warsaw and lived with his grandparents in Kolbuszowa in south-eastern Poland, where he also became involved in anti-Nazi resistance. Sometime early in 1940 he joined the Union of Armed Struggle, a precursor organization of the Home Army. In March 1941 he became a member of the Gray Ranks, a paramilitary underground scouting organization which carried out sabotage and diversion against the Germans. In particular, Bytnar and his cell focused on so-called "small sabotage" as part of the Wawer Group.