Nehemiah 4:18

For the builders had everyone his sword girded by his side,
and so builded
Thus accoutred he wrought, and was prepared for either service:

and he that sounded the trumpet was by me;
to give the alarm of war, that everyone might lay aside his work, and prepare for the battle: this officer stood by Nehemiah, that when he found it necessary, might give him orders to sound his trumpet, for the men to gather to him.