יהושע, פרק ח׳, פסוק ה׳

The battle plan for the city of Ai relies on a carefully crafted military deception, using the memory of past events to set a trap for the enemy. Joshua and the main body of the army will approach the city to lay siege to it once again [ביאור שטיינזלץ]. During this maneuver, Joshua himself will stand at the very front, directly facing the enemy forces as they enter the battlefield [מלבי״ם]. The strategic assumption is that since the men of Ai confidently came out to fight during the first encounter, they will certainly do so again [מלבי״ם].

The moment the enemy launches their attack, the Israelites will turn and flee [מצודת ציון]. The primary approach among commentators is that this flight is entirely different from their previous encounter. While the first battle resulted in a genuine defeat where the men of Ai struck the Israelites and chased them away, this time the retreat is strictly an illusion. It is a calculated move designed to deceive the enemy and draw them completely out of their fortified city.