On this day in 585BC, ancient precursors of the Iranian and Turkish people squared off for battle, along the banks of the River Halys in modern Turkey. They were the Medes and the Lydians. They had been fighting one another for more than 15 years.
A total eclipse of the sun occurred sometime during the battle, causing both Kings and both armies to immediately cease fighting and lay down their weapons.
The Greek historian Herodotus wrote that Thales of Miletus had predicted the eclipse in a year when the Medians and the Lydians were at war. It’s possible to calculate the date with precision because you can run the “solar clock” backwards as well as forward, and May 28 became one of the cardinal dates from which other dates in antiquity are calculated.
This wasn’t the first recorded solar eclipse, just the first to have been predicted beforehand. Two Chinese astrologers had lost their heads for failing to predict one, back in the 22nd or 23rd century BC. Clay tablets from Babylon record an eclipse in Ugarit in 1375 BC. Other records report solar eclipses which “turned day into night” in 1063 and 763 BC.
Predicting a solar eclipse isn’t the same as predicting a lunar eclipse; the calculations are far more difficult. When the moon passes through the shadow of the sun, the event can be seen by half of the planet, the total eclipse phase lasting over an hour. In a solar eclipse, the shadow of the moon occupies only a narrow path, and the total eclipse phase is only about 7½ minutes at any given place.
The method Thales used to make his prediction is unknown, and there is no record of the ancient Greeks predicting any further eclipses. It’s possible that he borrowed his prediction from Egyptian astrologers, using their techniques of land measurement (geo metry in Greek), later codified by Euclid and loved by 8th graders the world over.
Be that as it may, for the first time in history a full eclipse of the sun had been predicted beforehand. The Battle of Halys marked the first time in history, that a war was ended when day turned to night. Aylattes, King of Lydia, and Cyaxares, King of the Medes, put down their weapons and declared a truce, and their soldiers followed suit. The kings of Cilicia and Babylon helped negotiate a more permanent treaty. Alyattes’ daughter Aryenis married Cyaxares’ son Astyages to seal the bargain, and the Halys River, now known as the River Kızılırmak, was agreed to be the border between the two peoples.