The Battle of Bu'ath was the climax of a civil war between the two Arab tribes of Yathrib (later Madinah), the Aws and the Khazraj. The war had lasted more than ten years. It began as small clashes over land, water and grazing rights, which grew until they ended in this major battle. Most of the senior leaders of both tribes were killed. Those left were mostly younger men, tired of a decade of bloodshed. The one senior leader still standing was Abdullah ibn Ubayy ibn Salul.
By decimating the old leadership of the Aws and Khazraj, Bu'ath left the younger survivors receptive to something new, clearing the way for the reception of Islam in Yathrib soon after.
Other events recorded around the same time. Their order within the year is not established; use the storyline above for the sequence.
The Day of Bu'ath was a gift from Allah to the Prophet ﷺ. It was because of Bu'ath that their (the Aws and Khazraj's) unity had been fragmented and their leaders completely decimated.
A later reflection on the significance of the battle.