Here "he" refers to Othniel who represents himself and the army of Israel. Alternate translation: "Othniel and the Israelite soldiers went to fight against the army of Cushan-Rishathaim" (See: [[rc://en/ta/man/translate/figs-synecdoche]])
Here "Cushan-Rishathaim" represents his army. Alternate translation: "Yahweh helped the Israelite army defeat the army of Cushan-Rishathaim king of Aram" (See: [[rc://en/ta/man/translate/figs-synecdoche]])