Joshua 6:2

‘ And YHWH said to Joshua, “See, I have given into your hand Jericho, and its king, and the mighty men of valour.” '

The problem for Joshua was how the Israelites could breach the walls with the means that they had at their disposal. Spears and swords would have had little effect on them. But as he was pondering the situation YHWH promised him that it was given to him by YHWH, and that its king and its soldiery would shortly be in his hands. What was to happen would be decisive for the future. As the news of it spread around (Joshua 9:3) the Canaanites would realise that it was pointless to remain shut up in their cities as Yahweh could soon demolish their walls. It affected their whole military strategy. This may explain why they always left their cities to face Israel.