The Battle of Aroer was fought in 1188 BC when the Israelite judge Jephthah defeated the Ammonites and delivered his people from their oppression.
After 22 years of peace under Jair, the Israelites again turned to sin in 1206 BC, worshipping the Baals and Astartes and the gods of Aram, Sidon, Moab, the Ammonites, and the Philistines. God was said to have punished them with subjugation at the hands of the Ammonites for 18 years, and the Ammonites repeatedly crossed the Jordan and fought against Judah, Benjamin, and Ephraim, greatly distressing Israel. In 1188 BC, the Israelites called out for God, who sent them Jephthah to deliver them. The Ammonites once again planned an invasion of Israel from Gilead, while the Israelites encamped at Mizpah, where they were joined by Jephthah, a brigand and the son of a prostitute. Jephthah took command of the Israelites after they agreed to give him supreme command, and he in turn promised to sacrifice the first thing to leave his house on his triumphant return home. Jephthah marched his army from Mizpah to meet the Ammonites in battle, and he inflicted a massive defeat on them from Aroer to the vicinity of Minnith, twenty towns, and as far as Abel-keramim. The Ammonites were subdued before the people of Israel, ushering in several decades of peace.