A look at the book of Judges- 2- Othniel
Thus the children of Israel dwelt among the Canaanites, the Hittites, the Amorites, the Perizzites, the Hivites, and the Jebusites.
And they took their daughters to be their wives, and gave their daughters to their sons; and they served their gods. So the children of Israel did evil in the sight of the LORD. They forgot the LORD their God, and served the Baals and Asherahs. Therefore the anger of the LORD was hot against Israel, and He sold them into the hand of Cushan-Rishathaim king of Mesopotamia; and the children of Israel served Cushan-Rishathaim eight years. When the children of Israel cried out to the LORD, the LORD raised up a deliverer for the children of Israel, who delivered them: Othniel the son of Kenaz, Caleb's younger brother. The Spirit of the LORD came upon him, and he judged Israel. He went out to war, and the LORD delivered Cushan-Rishathaim king of Mesopotamia into his hand; and his hand prevailed over Cushan-Rishathaim. So the land had rest for forty years. Then Othniel the son of Kenaz died. (Judges 3:5-11) (NKJV)
When the Israelites were travelling to Canaan from Egypt, God had warned them through Moses,
Take heed to yourself, lest you make a covenant with the inhabitants of the land where you are going, lest it be a snare in your midst. But you shall destroy their altars, break their sacred pillars, and cut down their wooden images (for you shall worship no other god, for the LORD, whose name is Jealous, is a jealous God), lest you make a covenant with the inhabitants of the land, and they play the harlot with their gods and make sacrifice to their gods, and one of them invites you and you eat of his sacrifice,
and you take of his daughters for your sons, and his daughters play the harlot with their gods and make your sons play the harlot with their gods. (Exodus 34:12-16)
The Israelites broke their covenant with God and made covenants with the inhabitants of Canaan and as God said, they were a snare to them.
8 years of punishment here for the Israelites for disobeying God. God sold them into the hands of the king of Mesopotamia. When distressed, they cried out to the LORD and he raised up a deliverer for them: Othniel the son of Kenaz who delivered them by warring with the enemy king and the land had rest for 40 years.
We read of Othniel in the book of Joshua:
Caleb said, "He who attacks Kirjath Sepher and takes it, to him I will give Achsah my daughter as wife." So Othniel the son of Kenaz, the brother of Caleb, took it; and he gave him Achsah his daughter as wife. (Joshua 15:16,17).
The same has been mentioned in Judges Chapter 1.
Caleb was a warrior and wanted his son-in-law to be one as well. So he put forth a challenge and Othniel took it up. God gave him victory and Caleb's daughter Achsah became his wife.
Watch, stand fast in the faith, be brave, be strong. (1 Corinthians 16:13)