The Battle of Adasa was fought in 13th of the month Adar, 161 BC at Adasa (Hebrew: חדשה), near Beth-horon, between the Maccabees of Judas Maccabeus and the Seleucid Empire, whose army was led by Nicanor. Maccabeus won this battle, while Nicanor was killed. For a few years this day was celebrated as the "Day of Nicanor" (13th of Adar) to commemorate this victory. Despite the victory, within less than a year Judas Maccabeus was defeated and killed, fighting the Seleucids at Elasa. The Maccabees however continued to execute authority over Judea and led to a complete expulsion of Seleucid forces from the region.
Nicanor proceeded to the region of Beth-horon, northwest of Jerusalem, a place situated favorably for the Jews, who were acquainted with the country; Judas encamped against him at Adasa. According to 2 Maccabees 15, Judas inspired his troops by relating to them a dream-vision he had experienced, wherein the Prophet Jeremiah presented a gold sword to him and said, "Accept this holy sword as a gift from God; with it you shall crush your adversaries." (2 Maccabees 15:15-16, NAB). The battle that ensued was desperate, and ended in a glorious victory for the Jews; Nicanor fell, and his troops to the number of 9,000 were put to flight. Judas appointed the 13th of Adar, the day of the victory (161 BC), as a feast-day, and it still has a place in the calendar of special days ("Megillat Ta'anit").