The Papal or Western Schism lasted from 1378 to 1417 between those who supported the Papal claimants in Rome and Avignon (and, from 1409, Pisa). I know the map generally given is slightly inaccurate. And I also know the allegiance of certain realms to certain popes had just as much, if not more, to do with politics as with religion. But the basic gist of my question is this:
If, say, during this time period, a kingdom which supported the Roman pope wanted to make an alliance (formal or marriage) with a country that supported the Avignon pope, or vice versa, would there have been religious difficulties preventing it, like an alliance between a Catholic and a Protestant kingdom? And could they backtrack easily?
I'll admit, this isn't my normal area of expertise, so any opinions would be highly appreciated.