Tensions are escalating sharply between Saudi Arabia and Iran after Houthi rebels in Yemen launched a ballistic missile toward the Saudi capital, Riyadh, over the weekend. On Monday, Saudi Arabia said the missile launch constituted an “act of war” by Iran. The Saudis accuse Iran of backing Yemen’s Houthi rebels. Saudi Arabia’s accusation escalates the possibility of a direct military confrontation between the two regional powers. This comes as at least 11 top Saudi elites and officials were arrested in a widening crackdown aimed at consolidating the power of Crown Prince Mohammed bin Salman, who has been presiding over the U.S.-backed, Saudi-led war in Yemen.