After three years on the throne, King Salman bin Abdul-Aziz Al Saud and his son Crown Prince Mohammed bin Salman are pursuing the most aggressively sectarian and anti-Iran policy in modern Saudi history. The Wahhabi clerical establishment is an enthusiastic partner, which is good internal politics for the royals.

The Saudi antipathy for Shiite Iran predates the Islamic Revolution. The Saudis distrusted the shah and his imperial ambitions, and the anti-monarchist ideology of the Islamic Republic has only worsened their relationship with Persia. But Kings Abdullah and Fahd sought a measure of detente with Iran even during the height of the Iran-Iraq War, fearing that animosity could spiral out of control. Abdullah even sent a Saudi Shiite diplomat to be ambassador to Tehran, the one and only time a Shiite has served as a Saudi ambassador. Salman severed relations completely after the execution of a Saudi Shiite cleric prompted demonstrations against the Saudi Embassy in Tehran.

Iran’s success in acquiring influence in Iraq, Syria and Lebanon has deeply disturbed the kingdom. The fear of a pro-Iranian regime led by the Zaydi Shiite Houthis prompted the Saudi intervention in Yemen three years ago. The war is a proxy conflict between Riyadh and Tehran, stuck in a stalemate that costs the Saudis billions every month and Tehran next to nothing. More than a million Yemeni refugees are now in Saudi Arabia, according to the Saudi foreign minister, adding to the costs of the conflict. The pro-Saudi government has been effectively ousted from Aden by southern separatists and the world increasingly blames Saudi Arabia for the humanitarian catastrophe in the country. As a consequence, the Saudis have adjusted the blockade of the country marginally this year.

But the conflict is popular with Saudi clerics, who have long sought to strengthen Sunni Salafist groups in Yemen. In Mahra province in southeast Yemen, the Saudis have set up a Salafist missionary center to propagate Wahhabism, a move that has alarmed the Omanis next door. Senior clerics in Mecca regularly praise the king for fighting the Zaydis. Prince Mohammed is the face of the war as defense minister.