Could Lebanon divide on sectarian lines again?

The resignation of Saad Hariri as Lebanon's prime minister has upended the country's political establishment and escalated a war of words between Saudi Arabia and Iran.

In Riyadh, key government figures have accused the Iran-backed Shiite group Hezbollah of destabilizing Lebanon. Gulf Affairs Minister Thamer al-Sabhan said Hezbollah had engaged in acts of "aggression" that amount to a "declaration of war against Saudi Arabia."

Read more: Hezbollah's new 'power' threatens Israel

Hezbollah has likewise accused the group's rivals in Riyadh of meddling in Lebanon's internal affairs, alleging that "the resignation was a Saudi decision that was imposed on Prime Minister Hariri."

The back-and-forth between Sunni-ruled Saudi Arabia and Hezbollah could signal the further spreading of a feud between Saudi Arabia and Shiite-dominated Iran that has engulfed countries across the Middle East — including Yemen and Syria.

'Far more assertive'

Though Saudi Arabia has had limited success with its three-year military intervention against Iran-backed Houthi rebels in Yemen, the anti-government forces it supports in Syria have repeatedly been thwarted as the regime of Bashar al-Assad continues to make gains with the help of Russia and Iran.

Though he prefaced his remarks by saying Saudi Arabia would have unclear motives for interfering, Yezid Sayigh, a senior fellow at the Beirut-based Carnegie Middle East Center, said that, "as in Syria," any attempts to meddle in Lebanon's politics could backfire.

Sayigh told DW that Saudi Arabia could "end up triggering a crisis that actually produces opposite results in Lebanon," in large part because Iran would respond if its interests in the country were threatened.

Read more: Opinion: Saudi Arabia, the inscrutable kingdom

"The Saudis have always had a low-key approach to foreign policy, and have sought friends and used soft power and so on," Sayigh said. "Now, for the last few years, increasingly they have shifted to what is known as hard power and a far more assertive foreign policy. The problem in the last two years is that this is being conducted by someone with very little experience and who is bold — and that's not always a bad thing — but the boldness has already cost a devastating war in Yemen. The consequences for Saudi Arabia are going to be long-term."

Riyadh to Washington

Should Lebanon's political crisis turn violent, the resulting conflict could draw the United States and Israel into a deeper feud playing out across the Middle East. Israeli, Saudi and US officials view Iran as the premier "state sponsor of terrorism."

Read more: Is Saudi Arabia waging war on its Shiite minority?

Saudi Arabia has been keen to represent Iran as the prime source of conflict in the Middle East, especially as US President Donald Trump has increasingly postured against the country.

For Israel, Hezbollah represents a security threat on its border. The United States has branded it a "terrorist group."

Sayigh said the coming weeks and months would be telling, especially should the US recommend further sanctions against Iran.

Troubled history

Politically, Lebanon is divided along sectarian lines, with power distributed among the country's major religious groups.

Under a 1943 agreement following Lebanon's independence from France, the presidency is held by a Maronite Christian, the prime minister must be a Sunni Muslim, and the speaker of parliament is a Shiite Muslim. Since an agreement to end the 15-year civil conflict in 1990, the confessional system has continued to work with relative success.

Read more: Fragmented visions of Middle East prevail

The former prime minister's father, Rafik Hariri, was assassinated in 2005. After a lengthy investigation, a UN-backed tribunal issued arrest warrants for four Hezbollah members, implicating the militants in the murder. The group denies any involvement.