Mursili I Sacks Babylon

In 1595 BCE, Hittite king Mursili I led his army on an absolutely wild 1,000-mile campaign from Anatolia all the way to Babylon, sacked the city, ended the Amorite dynasty that Hammurabi had founded, and then just... left. Didn't even try to hold it. It was a pure power move that shocked the ancient world and created a power vacuum in Mesopotamia. The Kassites eventually filled it, but the flex was legendary.