The Battle of Muye was fought between the tribes of Zhou against the Shang Dynasty for control over China. The Zhou army consisted of 50,000 skilled soldiers, while the much stronger Shang forces exceeded 530,000, with an additional 170,000 armed slaves. The Shang slaves defected to the Zhou, which greatly demoralized the remaining soldiers, many of whom also defected. The ensuing battle was fierce, and the Shang forces were easily defeated by the better-trained Zhou.Here.
When the battle was over, the Shang Dynasty was destroyed, and the Zhou Dynasty was established. King Di Xin of the Shang Dynasty immolated himself following the defeat, leaving China open for rule by the Zhou. The Zhou Dynasty holds the distinction of being the longest-reigning dynasty in Chinese history.
Nice quick read on ancient battles. Good stuff.