At the United Nations Security Council on Monday, the United States proposed what Sudan’s war urgently requires: extending the U.N. arms embargo from Darfur to the entire country and explicitly bringing drones and related technologies within its scope. The existing measures expire on Sept. 12. The Council must act now; the case is overwhelming.

Start with an elementary principle: The map of an arms embargo should match the map of the war it is meant to restrain. When the Security Council strengthened the Darfur embargo through Resolution 1591 in March 2005, the mass atrocities driving international action were concentrated there. Months earlier, the U.S. had determined that genocide was being committed in Darfur.