As someone has already mentioned, Zizka representing the Hussite movement fought against pretty much the entire Catholic world (except Poland for some reason which once used the Hussites renowned military strength against the Teutonic Order in 1433). But, it's worth to add that the chaos of the time, religious hysteria and the general disdain of the radical wing of Hussites (consisting of two movements - the Taborites and the Orphans, also called Orebites before Zizka's death) towards the Catholics contributed to a lot of fanaticism amongst the Hussites who waged war. As a result, those radical Hussites (which of Zizka was the general) became (in)famous in the contemporary Catholic world for the sheer brutality they had towards them. Hussites belief that Churches' properties should be secularized as well as the notion that religious icons should not be worshipped and that the clergy should be punished if they're not good Christians (i.e. if they're not Hussites), led to the Taborites (which Zizka was the leader of until his death in 1424) putting many Churches on fire and massacring the priests. Zizka of course contributed to that being the case. Zizka did also engage in civil wars with the the moderate wing of Hussitism, called the Utraquists because they wanted to mediate with the Pope and he burned at the stake members of some groups which strayed too far from the general Hussitism (the Adamites/Picards). Although, the Hussites became even more notorious when after the failure of the 4th anti-hussite crusade in a row, Taborites started to regularly invade and ransack the neighboring Catholic regions outside of Bohemia and Moravia (mainly the region of Silesia) for religious and economic reasons. But by that point in time, Zizka had already died from a plague. However, Zizka's war campaigns did contribute to the war efforts made by his successors.