Turtledove, Harry. "Counting Potsherds"
Divergence: 480 BCE
What if: Xerxes led the Persians to victory over the Greeks, thereby preventing the spread of democracy.
Summary: Several hundred years later, a Persian court eunuch is sent to Greece to learn the name of the Greek king defeated by Xerxes.
Published: In Amazing Stories, March 1989; What Might Have Been? Volume 1: Alternate Empires (eds. Gregory Benford and Martin H. Greenberg), q.v.; and Departures, q.v.