The uniting force of the anti-fascist partisans on the territory was People's Liberation Army and Partisan detachments of Yugoslavia (NOV i POJ; Narodnooslobodilačka vojska i partizanski odredi Jugoslavije) under the command of Josip Broz (who went by the nom de guerre of Tito) and the Yugoslav Communist Party.
Smaller-scale partisan units such as the TIGR of the Primorje Slovenes were also integrated in the NLA eventually. The Chetniks, who also led a guerilla war on the Yugoslav territory, actually fought against the Partisans during most of the war.
The Partisans had the support of the Allies, both the western ones and the Soviet Union whose Red Army facilitated the liberation. However, the amount of organization among the NLA and the favorable position of Yugoslavia in Europe resulted in the country being one of the few Axis-occupied European countries to mostly liberate itself and not be encumbered by foreign army presence after the end of the war.