In the early morning of May 9, 2008, the Lebanese Shiite militia Hezbollah dispatched hundreds of heavily armed fighters to Beirut, and within twelve hours it had altered Lebanon’s political balance. Hezbollah and its allies quickly routed Sunni militiamen, took control of their political offices, and shut down media outlets owned by a prominent Sunni leader. The Lebanese government was paralyzed, while the Lebanese Army stood on the sidelines.

With the wave of revolution and violence that has engulfed the Middle East in the seven years since that day, Hezbollah’s actions are now largely a footnote. But, in retrospect, the events of May, 2008, were one of the opening salvos in the proxy war between Saudi Arabia and Iran. While the two powers were already fighting through proxies in Iraq, Hezbollah’s brief takeover of Beirut—and the events that led to it—took the conflict to a new battlefield and helped to define what would unfold in the region over the coming years: sectarian bloodletting and an expanding proxy war that now extends through Syria, Iraq, Yemen, the rest of Lebanon, and Bahrain.

After the Bush Administration invaded Iraq and ousted the Baathist regime, in 2003, both Iran and Saudi Arabia realized that there would be a power vacuum in Iraq, and they began jockeying to fill it. Neighboring Sunni regimes backed Sunni fighters and tribes, while Iran supported Shiite militias and the central Baghdad government. The House of Saud, which had long viewed Iraq as a bulwark against Iranian influence, tried to destabilize the Shiite-led government. Beyond Iraq, the Sunni Arab states were nervous about Iran’s growing regional power: its nuclear program, its support for Hezbollah and Hamas, and its alliance with Syria’s Bashar al-Assad.

In Lebanon, an alliance between Washington and authoritarian Sunni Arab regimes—Saudi Arabia, other Gulf countries, and Egypt—supported a Sunni-led government against Hezbollah, a political party and militia that is funded by Iran but also has deep roots in Lebanon’s Shiite community. The crisis in Lebanon began in February, 2005, with the assassination of the former Prime Minister Rafik Hariri, a billionaire construction tycoon who was the country’s most prominent Sunni leader and a longtime Saudi ally. His murder cleaved Lebanon into pro-Saudi and pro-Iranian factions. At the time, Hezbollah offered an alternative to Arab rulers placating the United States.

Hezbollah’s strong performance against a far superior Israeli military during their war in the summer of 2006 electrified the Arab world. That November, after talks between Hezbollah and the U.S.- and Saudi-backed Prime Minister, Fouad Siniora, failed, six ministers representing the Party and its allies resigned from the cabinet. Hezbollah and its Christian supporters then launched a nonviolent protest in downtown Beirut, erecting hundreds of tents outside the main government palace and holding large demonstrations demanding Siniora’s resignation. Lebanese Sunnis and several Christian factions united around Siniora, while the United States and Sunni Arab regimes rushed to support him.

In April, 2008, Western-backed Lebanese politicians discovered that Hezbollah had a secret fiber-optic communications network, and they quickly passed along details, including a map tracing the route, to the United States, France, Saudi Arabia, and other allies. “Iran Telecom is taking over the country!” Marwan Hamadeh, the Lebanese telecommunications minister at the time, told officials at the U.S. Embassy, according to a diplomatic cable released by WikiLeaks. Hamadeh told the diplomats that when the Sunni leader Saad Hariri—the son of Prime Minister Hariri and the main Saudi ally in Lebanon—first heard about Hezbollah’s network, he “sent a private plane from Saudi Arabia to pick up a copy of the map” so that he could share it with the Saudi king and intelligence chief.

The fiber-optic network, Hamadeh told U.S. diplomats, was built “under the radar,” with help from municipal officials, and was financed by the Iranian Fund for the Reconstruction of Lebanon, which had been rebuilding roads and bridges destroyed by Israel during the 2006 war. Hamadeh’s comments underscored that Saudi allies in Lebanon saw Hezbollah’s network as part of a larger, almost existential, threat from Iran. “Hamadeh highlights the system as a strategic victory for Iran, since it creates an important Iranian outpost in Lebanon, bypassing Syria,” the cable said. “He sees the value for the Iranians as strategic, rather than technical or economic. The value for Hizballah is the final step in creating a nation state. Hizballah now has an army and weapons; a television station; an education system; hospitals; social services; a financial system; and a telecommunications system.”

On May 6, 2008, Siniora and his cabinet issued one order outlawing the fiber-optic network and another dismissing the security chief at the Beirut airport, who was an ally of the Party. Hezbollah accused the United States and Israel of instigating the two decisions, and demanded that they be rescinded. On May 7th, fighting broke out between Hezbollah’s allies and supporters of Hariri. By May 9th, Hezbollah had deployed hundreds of fighters to the largely Sunni areas of West Beirut, routing Hariri’s partisans within hours and shutting down his newspaper and television stations. On May 15th, Siniora’s government rescinded its orders, Hezbollah pulled its fighters off the streets, and leaders of the two factions headed to Qatar to negotiate under the Arab League’s auspices.

At the time, I was in Beirut, staying in a neighborhood that housed an office belonging to Hariri’s political party, the Future Movement. There were often armed men milling outside the building. On the morning of May 9th, after a night of sporadic gunfire and rocket-propelled grenades, I saw a group of Hezbollah fighters moving toward the office. Three commandos in gray-green fatigues crouched, assault rifles propped on their knees, in a small garden where kids usually played soccer. Two more advanced methodically down the block, moving in military formation, shouting, “Don’t go outside! Stay inside! Don’t go out on your balconies!” A teen-age boy ran toward them, surrendering, with his hands raised above his head. He was barefoot and shirtless, to show he was unarmed.

Hezbollah’s quick success alarmed Saudi Arabia, which had poured tens of millions of dollars into funding Hariri’s political party and arming his allies in the Lebanese security forces. The day after Hezbollah’s takeover, the banner headline on the Saudi-owned pan-Arab newspaper Asharq Al-Awsat proclaimed, “Beirut Under the Second Occupation,” a reference to the Israeli siege and occupation of Beirut, in 1982.

The Saudi regime was so worried about Hezbollah and the perceived Iranian victory in Lebanon that Saudi leaders proposed creating an Arab military force, backed by Washington and NATO, to intervene in Beirut, according to another classified U.S. diplomatic cable disclosed by WikiLeaks. Prince Saud al-Faisal, then the Saudi Foreign Minister, floated the idea on March 10th to the U.S. special adviser on Iraq, David Satterfield, who was visiting Riyadh. Saud “stated that the effort by ‘Hizballah and Iran’ to take over Beirut was the first step in a process that would lead to the overthrow of the Siniora government and an ‘Iranian takeover of all Lebanon,’ ” the cable said. “Such a victory, combined with Iranian actions in Iraq and on the Palestinian front, would be a disaster for the US and the entire region.”

Saud said that the Arab force would be drawn from Arab “periphery” states—meaning not Saudi or other Gulf troops—and would be deployed to Beirut under the “cover” of the United Nations. “The US and NATO would be asked to provide equipment for such a force,” the cable said, “as well as logistics, movement support, and ‘naval and air cover.’ ” Saud also argued that the conflict in Lebanon would be an “easier battle to win” than trying to scale back Iranian influence in Iraq and the Palestinian territories.

Satterfield and other U.S. officials were skeptical of the Saudi proposal, and the idea soon died. But it marked a moment when both Iran and Saudi Arabia began to see their rivalry as a winner-take-all conflict. If Hezbollah gains an upper hand in Lebanon, then the Sunnis of Lebanon—and, by extension, their Saudi patrons—lose a round to Iran. If a Shiite-led government solidifies its control of Iraq, then Iran will have won another round. So the House of Saud rushes to shore up its allies in Lebanon, Syria, Bahrain, and Yemen.

Now Saudi Arabia has a new monarch, King Salman, who rose to power after his brother’s death, in January, and inherited the Saudi policy of containing Iran and of countering revolutionary sentiment throughout the region. Salman is more eager to intervene directly in the proxy battles with Iran, as he has done with the Saudi-led war against Houthi rebels in Yemen.

Prompted by Saudi Arabia, Arab states agreed at a summit in March to create a joint military force, mainly to counter Iran. It’s the same kind of Arab security force that Prince Saud proposed to U.S. officials in May, 2008, to scale back Hezbollah’s gains in Lebanon. But, reflecting the Saudis’ new aggressiveness, this force would not be reliant on U.S. and NATO air and naval power, nor would it seek political cover from the United Nations before intervening in Arab states threatened by insurgencies or Iranian influence, real or perceived. That is the new status quo in the region: both Iran and Saudi Arabia have hardened their positions into an open-ended conflict, and the people of Iraq, Syria, and Yemen are paying the price.