Yemen's war was supposed to be winding down. Instead, it is crossing borders again. The Saudi-Houthi conflict has entered a dangerous new phase. Fighting is now spilling across the Yemen-Saudi frontier. Riyadh has sent in its F-15s to pound Houthi positions. The Houthis have answered with missiles and drones aimed at Saudi soil. And then, the boldest claim yet. The Houthis say they shot down a Saudi F-15 over Marib. Riyadh has not confirmed it. No one has independently verified it. But in this war, perception is a weapon too, and the Houthis know it.