Of the middle watch, i.e. of the second watch; for though afterwards the night was divided into four watches by the Romans, Matthew 14:25, yet in more ancient times, and in the eastern parts, it was divided into three. He chose the dark and dead of the night to increase their terror by the trumpets, whose sound would then be loudest and best heard, and the lamps, whose light would then shine most brightly, and seem biggest, to surprise them at disadvantage, and to conceal the smallness of their numbers.
Related Commentaries of Judges 7:19
Judges 7:19
19 So Gideon, and the hundred men that were with him, came unto the outside of the camp in the beginning of the middle watch; and they had but newly set the watch: and they blew the trumpets, and brake the pitchers that were in their hands.