Yehoshua sent a small army of 3000 soldiers to conquer Ai, expecting it to be an easy victory like their conquest of Jericho. However, the Israelites were defeated in battle due to the sins of Achan, who had stolen valuables dedicated to God. Yehoshua devised a plan where his army pretended to flee to draw the army of Ai out of their city, then circled back to ambush them and burn the now unguarded city to the ground, securing an important victory for the Israelites.