Trumpet used for Sounding for a Memorial when the People Went Into Battle
Source: TTT
Numbers 10:9
When you enter into battle in your land against an adversary who attacks you, sound short blasts on the trumpets, and you will be remembered before the LORD your God and saved from your enemies.
Numbers 31:6, 7
And Moses sent the thousand from each tribe into battle, along with Phinehas son of Eleazar the priest, who took with him the vessels of the sanctuary and the trumpets for signaling. / Then they waged war against Midian, as the LORD had commanded Moses, and they killed every male.