From The Stream:

What did those countries where the Nazis saw armed resistance have in common? The resistance forces had access to private weapons. Polish resistance forces such as the Home Army had stored caches of military-grade weapons before the country’s final surrender. Jewish militias that would later rise up in the Warsaw ghetto had also obtained weapons, sometimes from other sympathetic Poles. In Yugoslavia, Ukraine, Belarus, and the parts of Western Russia that saw serious partisan activity, the resisters were also armed with leftover military weapons or smuggled arms from Stalin. French resistance forces — which only became a serious threat when Hitler broke his alliance with Stalin in 1941 and French Communists stopped collaborating — had stockpiled caches of arms, and received more via airdrops from Britain.