401 BC
Year 401 BC was a year of the pre-Julian Roman calendar. At the time, it was known as the Year of the Tribunate of Potitus, Cossus, Camillus, Ambustus, Mamercinus and Iullus (or, less frequently, year 353 Ab urbe condita). The denomination 401 BC for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.
Events
By place
Persian empire
Cyrus the Younger uses a quarrel with Tissaphernes over the Ionian cities as a pretext for gathering a large army and also pretends to prepare an expedition to Pisidia, in the Taurus Mountains. Cyrus starts out with about 20,000 men, of whom around 10,000 are Greek mercenaries. When he reaches the Euphrates River at Thapsacus, he announces that he is marching against Artaxerxes II. He advances unopposed into Babylonia; but Artaxerxes, warned at the last moment by Tissaphernes, hastily gathers an army. The two forces meet in the Battle of Cunaxa, north of Babylon, where Cyrus is slain.