On this day in 585 BC, after more than a decade of fighting, The Battle of Halys between the Central Asian Medes and Lydians was brought to an abrupt halt by a solar eclipse. It was the first eclipse known to have been predicted—and likely the first to have ended a war. The event is also known as the Battle of the Eclipse.
Prior to the eclipse, Aylattes, king of Lydia, and Cyaxares, king of Medes, had been at war for 15 years. Just before the eclipse occurred, they were battling near the Halys River in what is now central Turkey, according to historical reports. Suddenly, the skies darkened and the sun was obliterated. Stunned, both armies lay down their weapons. With that, the battle—and the war—was over, thanks to an astronomical intervention. The kings of Cilicia and Babylon helped negotiate a treaty between the enemies, and the Halys River where the Battle of the Eclipse was fought became the boundary between the two groups.
Though it was not the first recorded solar eclipse—earlier eclipses have been predicted (successfully or not) as early as 2300 BC in China and 1375 BC and 1063 BC in Babylon—historical records suggest this eclipse was the first to have been predicted. In written records, Greek historian Herodotus wrote that pre-Socratic Greek philosopher Thales of Miletus predicted that an eclipse would occur when the Medians and Lydians were at war. It is unknown which method Thales used to predict this eclipse. At the time, Greeks could not accurately predict eclipses—but the Egyptians could, and it’s likely Thales adopted their techniques. Solar eclipses are particularly difficult to predict. During lunar eclipses, the moon passes through the Earth’s large Sun shadow, so the event is visible on the entire side of the Earth that is experiencing night and usually lasts for more than an hour. But during solar eclipses, the moon’s shadow falls across the Earth in a much smaller area and the maximum duration of the eclipse in any given place is only about 7 and a half minutes. As such, Thales must have known the moon’s orbit in some detail to have predicted the eclipse.
However Thales calculated the famous eclipse, it was went down in history as the eclipse that ended a war.