Bible Verses About Trumpet: Used in war, of Abijah

"So look here! God is with us, leading us and his cohanim with the battle trumpets to sound an alarm against you. People of Isra'el! Don't fight against ADONAI, the God of your ancestors; because you will not succeed."

Thus when Y'hudah looked back, the battle had to be fought in front of them and behind them. They cried to ADONAI, and the cohanim sounded the trumpets.