The 15 battles fought at Adrianople:
- Fought between the Emperor Constantine and a pretender to the throne.
- The best-known Battle of Adrianople, in 378. Emperor Valens loses (disastrously) to the Goths.
- 718, the Bulgars foil a Muslim army's attempt on Constantinople.
- . . .
- and
- All battles fought by the Bulgars during their assaults on Constantinople, in 813, 914,and 1003.
- 1094, between the Byzantine throne and a usurper.
- The Bulgars defeat the Crusaders Baldwin (who had installed himself as Emperor of Byzantium) and Doge Dandolo of Venice in 1205.
- 1224, the newly restored Byzantine royal house beats the Bulgars.
- 1255, an engagement in a Byzantine civil war.
- 1355, the Byzantines beat the Serbs.
- 1365, the Ottoman Turks advance on Byzantium.
- 1829, the Russians seize the city (now known as Edirne) from the Ottoman Empire.
- . . . and
- In 1913, the Turks first lose the city to the Serbian-Bulgarian alliance, then regain it.
Why should this minor city (current pop. ~100,000) be the focus of so many battles (more, in fact, than any other place in history)? Geography. Edirne sits on the main land bridge between Southern Europe and West Asia, so that any army traveling in either direction must needs take the city. Not only that, it sits at the juncture of three rivers, which provide logical routes of invasion into Macedonia to the west, Bulgaria to the northwest, and the Black Sea coast to the north.
Information from John Keegan's A History of Warfare, p. 70. and thanks to legbagede for reminding me.