Yeah you're right that was the situation when Yugoslavia was unified Dinamo, Crvena Zvezda and Partizan had epic rivalries, especially in a nationalist way, Croatia and Serbia have had political power and ethnic problems for like the past 100 years.... As for the game you referred to it was in 1990 with Crvena Zvezda and Dinamo here in Zagreb, the riots that ensued where one of the worst in footballing history however political tension were already boiling over at that stage is too easy to blame that match, although in that iconic moment moment when Zvonimir Boban super kicked that Serb police officer beating the Dinamo fan with a nightstick, it symbolised Croatia desire to break away from communist yugoslavia. Now in these days yes, we are split into our own national leagues sure, and well Dinamo and Hajduk are traditionally Croatias big 2, but recently Croatian talent has been snapped up by England, Modric Corluka Eduardo from Dinamo, and Kalinic and Kranjcar from Haijduk so HNK Cibalia, and HNK Sibenik are Dinamos closest league rivals etc. Now umm, I am a post Yugoslav Croatian you know, even though I was born when Yugoslavia was still unified, but after 1995 Croatia was sovereign and independant.... So Croats that have grown in this time have a different mind than the older ones who lived through and remember the bad times. Its cool that you have took time to read on something like this, I guess you're an intelligent guy. Greetings from Zagreb