After Joshua died at the age of 110, and Israel had no leader, "the Israelites had offended the Lord by forgetting the Lord, their God, and serving the Baals and the Asherahs, the anger of the Lord flared up against them, and He allowed them to fall into the power of Cushan-rishathaim, king of Aram Naharaim, whom they served for eight years." (Judges 3:7-8).
A pattern set up after this where the Lord raised up Judges to deliver Israel from their oppressors, when the Israelites cried out to Him for help. Othniel was the first of the Judges.
Othniel was the son of Caleb's younger brother Kenaz, and "The Spirit of the Lord came upon him, and he judged Israel. When he went out to war, the Lord delivered Cushan-rishathaim, king of Aram, into his power, so that he made him subject. The land was at rest for 40 years, until Othniel, son of Kenaz, died." (Judges 3:10-11).
Othniel's defeat of Cushan-rishathaim was a great victory. But Othniel had another victory years earlier. When the Judahites were marching against the Canaanites, they came up against the inhabitants of Debir.
Caleb vowed to give his daughter, Achsah, in marriage to the one who attacks Debir and captures it. Responding to his uncle Caleb's challenge, Othniel captured Debir and restored it to the Israelites. And then wed Achsah.