I made a note about something, but now I can't find it. It was a major shift in the political situation of Europe in the late Middle Ages. Initially one country was the hegemon and the pope organized all of the others against it. Then another country became hegemon, and all of the powers were organized against that one. I think it was Germany, and then France, but I'm not sure when. It was sometime from 1250-1450.
I could be confusing it for something much later, but I don't think so.
Update: I suspect it may have had to do with the lowland countries, aka Holland, Belgium and Flanders. Western powers were allied against one country to prevent it from gaining control of it, and then against another country.