The Judean mountains present the next obstacle. If Israel can conquer them, then there bridgehead by the river will be safe. Not only that, but the Egyptians (who still used major trade routes near the coast) and Pheoniceans (Egypt’s allies on the coast) will be unlikely to waste time attacking.
Bethel is the biggest town, defending the watershed in the mountains, and therefore a major target, but it’s very well-defended. However, the watershed itself lies in Ai, so the Israelites head there first. However, the first, over-optimistic frontal attack fails.
Read Joshua 7:4
Failure’s not defeat of course. The Israelite’s second attack is more sophisticated and uses a two-pronged approach—one army hiding in the hills above Ai while the other pretends to attack and retreat.
Read Josh 8:14-19
Once the enemy has been drawn far enough away, Joshua gives the signal and the hidden army sets fire to the fort. The two branches of the army then trap Ai’s defenders between them, and the written report declares not a single enemy survived, as is the wont of written military reports, both then and in more modern times.