What does Numbers 31:6 mean?

Moses sent them into battle, along with Phinehas, the son of Eleazar the priest. Phinehas took with him some of the sacred objects and the trumpets for sounding the battle signal. Numbers 31:6 - Modern Text Bible

(Phinehas, a priest, goes with the army, carrying holy items and trumpets, showing that this is a religious mission as well as a military one.)