מלכים ב, פרק ג׳, פסוק ח׳

As the allied kings prepare to launch their military campaign, they must first agree on a route to the battlefield. A strategic planning session takes place between the leaders to determine the most effective path forward. During this discussion, the king of Israel asks for direction, and Jehoshaphat, the king of Judah, takes the lead in answering and mapping out the journey [מלבי״ם, ביאור שטיינזלץ]. He determines that the armies should march through the wilderness of Edom.

The primary approach among commentators is that this specific route was chosen first and foremost for political and military reasons. At that time, Edom was under the control of the kingdom of Judah. By marching through Edomite territory, the kings intended to draft the king of Edom and his forces into their campaign, relying on this extra support to swell the ranks of their army.

Beyond the clear advantage of gaining Edomite troops, this path also offered significant tactical and geographical benefits. Marching south into the desert could have served as a strategic maneuver to surprise the enemy, keeping the advancing forces hidden from view and preventing early detection [רלב״ג]. Furthermore, traveling deep into the southern wilderness of Edom before heading north may have been chosen because it was an easier path to navigate. It provided a much smoother journey compared to the difficult and complex task of crossing the Jordan River [ביאור שטיינזלץ].