Well, I was thaught in my primary school in then Yugoslavia, now Croatia, quite some time ago, that majority of members of all Yugoslavian nations - Serbs, Croats, Slovenians, Macedonians and Muslims (nowadays called Bosnians or Bosniaks), rose against traitorous, collaborationist official local regimes (both Croatian Ustaše and Serbian Četnici) which sided with fascists and nazis after king Peter II of Yugoslavia cowardly ran away to London. With help of our allies, UK, USA, France, Russia and others, we managed to liberate our country not only from temporary foreign nazi and fascist occupiers, but also from local parasites who lived on the back of working people - royalty, nobility, bankers, industrialists, capitalists etc.
Current mainstream global narative, along the lines of "Eurasia is in war with Eastasia. Eurasia has always been in war with Eastasia" is trying to convince me that the history I had been thought was a lie. So far I'm not convinced.
About PS: indeed, outfit looks similar (but not identical) to uniform of Yugoslav Pionir https://en.m.wikipedia.org/wiki/Union_of_Pioneers_of_Yugosla...