Jewish partisans fought in almost every country in Europe. There was partisan activity in Belgium, Poland, Russia (Belarus and Ukraine), France, Italy, Greece and Lithuania. The partisans hid their encampments in the forests, swamps and mountains.
Partisan activity was particularly intense in Eastern Europe. Russian partisan units in Eastern Europe were highly organized and trained people to use guns, to dynamite bridges, and operate in a military fashion. Military order was kept in these groups (you could be shot for falling asleep on guard duty).
Partisans in Yugoslavia and Italy ambushed Nazi convoys and drew German attention away from the front. Entire battalions were removed from the front lines to deal with the “partisan problem.” Entire battalions!