Suddenly (see remarks in Introduction on Joshua's characteristics as a general. Also Joshua 10:9). And they fell upon them. This phrase denotes the rapidity of the onset. While they deemed him to be leagues away, he suddenly appeared at the head of his army, no doubt debouching from one of the mountain passes of Upper Galilee; and before they could set themselves in battle array, his troops, without giving the enemy time to rally, or themselves a moment's breathing-time, commenced the attack.
The LXX. adds "in the hill country" here, an obvious blunder. The translator must have carelessly read בהר for בהם.