Is the Iran-Saudi Cold War Heating Up?

Throughout decades of ferocious rivalry, Iran and Saudi Arabia have, even while backing competing forces across the Middle East, generally maintained one red line: They wouldn’t interfere directly in each other’s domestic security. Policy makers in Riyadh and Tehran have known that backing militant groups among their rival’s Shiite minorities in Saudi Arabia or Sunni minorities in Iran could lead to an escalation for which neither country is ready. But that tacit agreement might be unraveling.