Lebanon is a tiny country, with a population of around six million; it could fit neatly between Philadelphia and Danbury, Connecticut. It has survived many crises over the past several decades: a brutal civil war from 1975 to 1990 that left 100,000 dead, a string of political assassinations since 2004 whose perpetrators have gone unpunished, and occupations by Israel and Syria. But Lebanon’s resilience is fraying. Its infrastructure is badly damaged and unemployment is high. It is also struggling to accommodate a large refugee population—500,000 Palestinians, many descended from those who fled the 1948 Arab-Israeli war, and nearly 1.5 million Syrians, a majority of them Sunni Muslims.

Most of the Syrian refugees I met in Lebanon do not want to be there—or in Turkey, Jordan, Iraq, or Egypt. They are fleeing intense fighting, ethnic cleansing, starvation, chemical attacks, and Russian air strikes that devastated Aleppo and other rebel-held areas. It is clear that they are not welcome in Lebanon, where they are increasingly seen as disrupting the country’s delicate sectarian balance among Shia Muslims, Druze, and Christians and as vulnerable to Islamist radicalization.

Lebanon’s most recent crisis was the sudden resignation of Prime Minister Saad Hariri on November 4 during a visit to Saudi Arabia. His announcement, in which he explained that he was afraid for his life, surprised even his closest advisers and rattled the country. He has since returned to Lebanon and has suspended his resignation. Hariri’s father, Rafik, a former prime minister and a prominent Sunni businessman, was assassinated in 2005, along with twenty-two others, when explosives hidden in a van were detonated as his motorcade drove near the St. Georges Hotel in Beirut. After a painful inquiry, the UN determined that the assassination was likely committed by members of Hezbollah with Syrian planning and logistical support. Hezbollah is the Shia political party and militant organization funded by Iran and Syria. Hariri’s death was followed by a series of sectarian murders of other anti-Syrian politicians, compounding the long-standing frustration with Lebanon’s failure to bring his killers to justice.

Hezbollah, which backed President Bashar al-Assad in the Syrian war, has attained so much power in Lebanon that it is considered a state within a state. It holds sway in parliament and is able to infiltrate Lebanese military intelligence. Meanwhile, Saudi Arabia, the regional Sunni giant emboldened by the Trump administration’s seal of approval, has a stake in keeping Sunnis prominent in the Lebanese government.

These rising tensions are part of a much larger conflict. Saudi Arabia and Iran, the regional Shia giant, are fighting proxy wars for influence in the Middle East. The bloodiest battlefield so far has been Syria. In Yemen, Iranian-backed Houthi rebels are fighting against forces loyal to the government of President Abdrabbuh Mansour Hadi, which is supported by Saudi…