The Catholic Church had nothing to do with it. Like most of Central Europe, Croatia was caught between two forms of evil, totalitarian socialism—Nazi and Communist. Pretty hard to distinguish between them. They were both amazingly evil, vile, and destructive.
As for the various killings, most of it was done by Stalin and Hitler. But they did stir up the old tribal hatreds in the region. Those were far from one sided. The Serbs, the Croats, and others had been killing each other for centuries, and who was originally responsible was pretty well lost in the sands of time.
Because the Communists and leftists have pretty much controlled the propaganda machines since Hitler went down, the Croats have gotten a worse rap than some of the others. Hard to justify. There’s plenty of blame to go around—not least against the invading Muslim hordes.
This wasn't about "tribal hatreds", Cicero. This was about a clerico-fascist regime:
Worldmark Encyclopedia of the Nations, Europe, edition 1995, page 91, entry: Croatia
Quote:
Slavko Kvaternik [the second in command to the Croatian WWII fuehrer, Dr Ante Pavelic] explained [on the day of formation of the WWII "Independent State of Croatia", on April 10, 1941] how pure Croatia should be built - by forcing one third of the Serbs to leave Croatia, one third to convert to Catholicism, and one third to be exterminated. Soon Ustasha bands initiated a bloody orgy of mass murder of Serbs unfortunate enough not to have converted or left Croatia on time. The enormity of such criminal behavior shocked even the conscience of German commanders...
Jasenovac was the only deathcamp in Europe NOT run by Nazi Germany, but instead was run by the Croatian Ustashi themselves.
The distance between Rome and Zagreb, Croatia is only a little over 300 miles. There were Papal legates, like the one pictured above back & forth between the two cities along with a few thousand Italian troops along the Coast. It is absolutely unbelievable that with hundreds of thousands of Serbs, Jews & Gypsies being massacred a few hundred miles away over the course of 4 years in the name of "a 100% Catholic Croatia", that "Pope Pius didn't know".
While he may not have been able to stop the Germans, he certainly could have stopped the forced conversions and the clerical participation and blessing of this mass murder, but instead he raised no objections. He just looked the other way.
It's for God to judge the full extent of Pius' sin, but to make Pius "a saint" is to degrade the Church itself.
And by the way, during WWII, the Croatian Ustahe regime made the Bosnian Muslims into "Honorary Croats"
The claim of centuries old hatred between Serbs and Croats is widespread, but it is not true. In the past, until XX century, there was no bloodletting between Serbs and Croats. Slight animosity existed due to different social position in the Austro-Hungarian empire, but not hatred because of killings. Croats even decided to adopt Serbian language as their own standard language. It could not be possible if there was centuries old hatred.
Also, it is worth noting that both Serbs and Croats are ancient peoples while Serbians and Croatians were nations created by the different political will. Croatians as a nation included ethnic Croats and all other Roman Catholics living in South Hungary. Serb living in South Hungary could declare himself to be Serb or Croatian, but not Serbian. Or, Croat living in Serbia could declare himself to be Serbian, but not a Serb. All this changed with WWI when driven by racist propaganda Croatians commited first large scale murders of Serbs on Austro-Hungarian territory and later, in Western Serbia.
It all got worse some 30 years later, with genocide of Serbs in Independent State of Croatia.This is all XX Century history and much of it living history. It is not ancient hatred at all.