Originally Posted by AmusedToDeath

Historically - no. There have been attempts of forced unification of ethnic Serbs in Croatia by converting them to catholicism, and that policy was encouraged by Vatican. Huge number of converted Serbs declare as Croats now.

However, the hate between the 2 peoples started to be strong during and after WW2, because Croats did some terrible crimes against Serbian population (see Jasenovac death camp) and it renewed in the 1990's. But the situation is much better now.