Eclipse of Thales

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The Battle of Halys, also known as the Battle of the Eclipse, took place at the Halys River (present-day "Kızılırmak" river in Turkey—(Zoomable Map centered at Mouth locus at 41.72° N 35.95° E ) on May 28, 585 BC between the Medes and the Lydians. The final battle of a fifteen-year war between Alyattes II of Lydia and Cyaxares of the Medes, the battle ended abruptly due to a total solar eclipse; the eclipse was perceived as an omen, indicating that the gods wanted the fighting to stop.


The war is thought to have started because of clashing interests in Anatolia; Herodotus (Histories, 1.73-74) claims, however, that some Scythian hunters employed by the Medes who once returned empty-handed were insulted by Cyaxares. In revenge the hunters slaughtered one of his sons and served him to the Medes. The hunters then fled to Sardis, the capital of the Lydians. When Cyaxares asked for the Scythians to be returned to him, Alyattes refused to hand them over; in response, the Medes invaded.


A truce was hastily arranged. As part of the terms of the agreement, Alyattes's daughter Aryenis was married to Cyaxares's son Astyages, and the river Halys was declared to be the border of the two warring nations.

The eclipse

According to Herodotus (1.74):

"In the sixth year a battle took place in which it happened, when the fight had begun, that suddenly the day became night. And this change of the day Thales the Milesian had foretold to the Ionians laying down as a limit this very year in which the change took place. The Lydians however and the Medes, when they saw that it had become night instead of day, ceased from their fighting and were much more eager both of them that peace should be made between them."

Since the exact dates of eclipses can be calculated, the Battle of the Eclipse is the earliest historical event of which the date is known with such precision.

According to NASA, the eclipse peaked over the Atlantic Ocean at 37°54′N 46°12′W / 37.9°N 46.2°W / 37.9; -46.2 and the umbral path reached south-western Anatolia in the evening hours, and the Halys River is just within the error margin for delta-T provided. [1]


  • G. B. Airy, On the Eclipses of Agathocles, Thales, and Xerxes, Philosophical Transactions of the Royal Society of London, Vol. 143, 1853, pp. 179-200
  • Alden A. Mosshammer, Thales' Eclipse, Transactions of the American Philological Association, Vol. 111, 1981, pp. 145-155