שופטים, פרק כ׳, פסוק ל״ח

A successful military operation against Gibeah required precise coordination between the main Israelite army and a hidden ambush unit. To ensure perfect synchronization during the attack, the two groups established a prearranged sign. Commentators agree that this sign served as a timing mechanism, communicating the exact moment the hidden soldiers infiltrated the city [מצודת דוד] and [מצודת ציון].

The plan dictated that once the ambush force breached the city walls, they would ignite a massive fire. They were instructed to increase the flames [מצודת ציון, ביאור שטיינזלץ] by specifically burning materials that would produce a heavy, thick smoke, ensuring the signal would be clearly visible from a great distance [מצודת דוד]. The nature of this visual cue is understood in slightly different ways. [רש"י] emphasizes the sheer height of the smoke. Meanwhile, [מצודת ציון] and [רד"ק] describe it as a distinct, towering pillar rising into the sky. Expanding on this, [רד"ק] suggests the signal could refer either to the visible flames of the beacon itself or to the resulting column of smoke. Ultimately, the action consisted of lighting a large, intentional smoke bonfire [ביאור שטיינזלץ].

From a tactical standpoint, this fire was the turning point of the battle. As soon as the ambush force captured the city and sent the smoke billowing upward, the message was successfully transmitted. The main Israelite fighters saw the smoke and instantly knew Gibeah had fallen. This was their awaited cue to stop their retreat, turn around, and launch a direct counterattack against the Benjaminite forces pursuing them [רש"י, רד"ק].