Though it is not recorded in Scripture, it is very likely that the Israelites would have heard rumours and news about the armies gathering in the north. They would have been told about the number of kings joining forces as well as the military equipment which they had. This would most certainly have been frightening to them since they were outnumbered and they could only fight on foot. They did not have horses or chariots.
6 And the LORD said to Joshua, “Do not be afraid of them, for tomorrow at this time I will give over all of them, slain, to Israel. You shall hamstring their horses and burn their chariots with fire.”