Judges 7:16, 19

He divided the three hundred men into three companies, and he put trumpets and empty pitchers into the hands of all of them, with torches inside the pitchers.

So Gideon and the hundred men who were with him came to the edge of the camp at the beginning of the middle watch, when the guards had just been changed, and they blew the trumpets and smashed the pitchers that were in their hands.