The night was likely divided into three watches of four hours each (8:00–12:00, 12:00–4:00, and 4:00–8:00), with a third of the army taking each watch. The second watch begins at midnight. At this changing of the guard, one third of the army would have been walking back to their tents; another third would have been asleep.
19 So Gideon and the hundred men who were with him came to the outskirts of the camp at the beginning of the middle watch, when they had just set the watch. And they blew the trumpets and smashed the jars that were in their hands.