Italian peninsular

Italy comprised lots of city states, e.g. Florence, Milan, Venice, and, of course, Rome. These states were usually competing with each other, sometimes in battle. On top of that, several foreign powers had interests in Italy. Aragon ruled the kingdoms of Naples and Sicily. France wanted them. So they  went to war (for more on which, click here.)

Since you don't need to know anything about the Italian wars, other than that they happened, the only rulers I'm giving you are the Popes.

Leo X with a couple of cardinals, by Raphael.

Leo spent loadsamoney, including on the rebuilding of St Peter's Basilica. This caused Luther to nail his 95 theses to a church door, and thus precipitated the Reformation.