The War of the League of Cambrai was fought from 1508-1516 by...basically everyone who had any interest in Italy at the time (which was most of Europe). It was a mess:
- It's been described by one period expert as "the least comprehensible war I’ve ever studied."
- Here on the stack, it's been mentioned that "most factions within the war were at one time allies and at others enemies."
- The list of belligerents on the Wikipedia page has to do some amusing contortions to correctly represent what side each country was on at any given time.
You get the idea.
The aforementioned Wikipedia article does a respectable job of covering when various states switched sides in the war, but is a little light on why. What was it that caused this war, in particular, to be so messy and confusing?