CAIRO — In a single day this week, the United States' involvement in Yemen's catastrophic six-year-long war pivoted. On Thursday, President Biden ended the remnants of U.S. support for a Saudi-led coalition's offensive operations in the conflict, pledged to intensify diplomatic efforts to halt the fighting and named a highly regarded new special envoy to the country.

Now comes the hard part.

Since 2015, when the U.S.-backed regional coalition headed by Saudi Arabia entered the war and propelled it into overdrive, Yemen has become the scene of a complex, intractable conflict that has killed tens of thousands and brought millions to the brink of starvation.

Today, it is an arena for multiple overlapping tussles over power, influence and ideology, fueled by regional players seeking to enhance their own strategic and security interests.

Even as it grapples with a severe humanitarian crisis, the Middle East’s poorest country is more fractured then ever along political, tribal, regional and religious lines. It also remains a haven for an al-Qaeda affiliate that has targeted the United States and Europe and capitalized on the instability generated by the conflict.

“Ending U.S. support won’t automatically mean an end to the war, at all,” tweeted Peter Salisbury, senior Yemen analyst at the International Crisis Group. “There is a really fine balance to be struck here, in finding a way to end the war that armed, political factions, local groups and civil society can buy into. Not easy at all.”

Thursday’s announcement in fact appeared to be largely political and symbolic, elevating the importance of ending Yemen’s war as a U.S. foreign policy priority and, in a departure from the Trump administration, potentially signaling the intent to invest major diplomatic weight in the effort to clinch a peace deal.

Yemen’s primary war pits northern Shiite rebels, known as Houthis, against Saudi Arabia, the United Arab Emirates and other regional Sunni powers that are ostensibly seeking to restore Yemen’s internationally recognized government. The conflict is also a regional one, in which the Saudis and Emirates are seeking to prevent Iran, which is aligned with the Houthis, from expanding its influence.

Then there is the U.S.-led counterterrorism war against al-Qaeda in the Arabian Peninsula, or AQAP, as the affiliate is known, and a smaller Islamic State presence. Here, the UAE and local proxies are helping the Pentagon but are also embroiled in other localized conflicts. To make it more confusing, the Houthis are also battling al-Qaeda and the Islamic State.

There are also deep divisions within the coalition. Rifts between southern separatists, backed by the UAE, and forces aligned with Yemen’s government, backed by Saudi Arabia, have led to fierce clashes over the past few years.

The separatists, who seek to split Yemen’s south from its north, have long been suspicious of the Yemeni government, which has been ruled for decades by northerners, although recently they have appeared to be cooperating again. The separatists and the UAE disapprove of Yemeni President Abed Rabbo Mansour Hadi’s alliance with al-Islah, an influential Islamist party with links to the Muslim Brotherhood, which the Emirati leadership views as a domestic threat and a radical force in the Arab world. 

Numerous diplomatic efforts by the United Nations and regional powers have failed, including U.N.-sponsored peace talks held in Kuwait in 2016. Since then, more armed groups have emerged and the Houthis have consolidated their power in the north, where most of Yemen’s roughly 30 million people live. 

“Yemen no longer functions as single country,” said Gregory Johnsen, a former U.N. investigator, in a tweet Thursday. “Yemen is Humpty Dumpty and it is not at all clear that it can be put back together again.”

Johnsen, who is also the author of “The Last Refuge: Yemen, al-Qaeda and America’s War in Arabia,” added: “No armed group in Yemen has enough guys or guns to impose its will on the rest of the country, but nearly every armed group has enough of both to act as a spoiler if they believe their desires aren’t being met.”

The Biden administration has appointed Tim Lenderking, a career diplomat who is well regarded by the United Nations, analysts and aid groups, as its new special envoy to Yemen.

“Our primary objective is to bring the parties together for a negotiated settlement that will end the war and the suffering of the Yemeni people,” a White House spokeswoman said in a statement. “This will be challenging, but we have to make it our priority.”

Thursday’s announcement also indicates a different approach to arms sales to Saudi Arabia, in which officials will evaluate proposed deals using the war in Yemen as a primary lens. Immediately, that means that two arms sales that the Trump administration notified Congress about in December, which included up to 3,000 GBU-39 bombs from U.S. firm Boeing and more than 7,000 Paveway munitions from the U.S. arms firm Raytheon, are no longer expected to proceed.

U.S. and Western aid groups working in Yemen are urging the administration to swiftly overturn the Trump administration’s partial suspension of aid last year in Houthi-controlled areas. The Biden administration on Friday notified Congress that it would reverse another Trump policy, the designation of the Houthis as a foreign terrorist organization, which could improve delivery of assistance to millions.

“The Biden Administration can make a dramatic impact on the humanitarian nightmare in Yemen by reversing this aid suspension immediately,” David Miliband, the head of the International Rescue Committee, said in a statement.

“The shift from a failed war strategy toward a comprehensive diplomatic approach cannot come a moment too soon,” he added.

Aid groups say recently issued licenses have allowed aid activity to continue for now but point to more worrying signs in Yemen’s finance sector and vital imports including fuel and medicine. “President Biden’s moves so far are welcomed and encouraging, but every day the designations remain in place is another day of uncertainty and adds to the risk that an already devastating crisis will dramatically worsen,” said Scott Paul, humanitarian policy lead for Oxfam America.

A key question is whether Yemen’s warring parties will accept the sharp turn in U.S. policy and view Washington as a neutral and trustworthy diplomatic broker.

U.S. bombs sold to Saudi Arabia and its allies have killed or injured thousands of Yemenis, according to human rights groups and eyewitnesses. In Houthi-controlled areas, the United States is viewed as a main instigator of the war. In Sanaa, Hodeida and other cities, walls are covered in graffiti depicting U.S. bombs and fighter jets killing Yemenis, among other unflattering images.

The United States will remain involved in counterterrorism operations against AQAP, which is likely to deepen anti-American sentiment among many Yemenis.

A big issue, analysts say, is the extent of the U.S. cutoff of support to Saudi Arabia.

The announcement is expected to have little practical effect on U.S. military operations related to the coalition’s war in Yemen, the bulk of which have already been scrapped. In 2018, amid a bipartisan congressional outcry over civilian casualties and Saudi operatives’ killing of Washington Post columnist Jamal Khashoggi, the Trump administration halted aerial refueling of Saudi and Emirati jets for the Houthi campaign.

While the White House spokeswoman said the shift would include “restricting our intelligence sharing arrangements with Saudi Arabia and the Saudi-led Coalition,” that sharing was already limited to providing Saudi officials information about direct threats against them, according to military officials.

It was not immediately clear what would happen with U.S. contracts to maintain American-made military equipment in Yemen, which includes F-15 and F-16 jets.

The Biden administration will presumably continue to assist the Saudis with their defense systems along the Yemeni border and air defenses against Houthi missile and drone assaults, said Gerald Feierstein, a former U.S. ambassador to Yemen.

“The impact of the decision is really more in terms of U.S. posture and signaling than it is in terms of actually impeding Saudi capabilities in Yemen,” Feierstein said in an email. “The President will make clear that the U.S. will emphasize a political strategy to end the conflict and wants Saudi support for achieving that.”

“In my view, the Saudis support an end to the conflict as well, as long as the resolution reflects their core security requirements,” he added.

But other analysts warned against replicating previous peace efforts that were widely criticized for leaving out the southerners and other Yemeni populations with grievances.

“The Biden [administration] need to understand that #Yemen war is much more complex & won’t be resolved through a political settlement between Houthis & Hadi govt,” tweeted Nadwa Dawsari, a nonresident scholar at the Middle East Institute in Washington.

“A political settlement under current conditions will be a quick win for western diplomacy,” she said in another tweet. “But it will reinforce the power dynamics that gave rise to the conflict, empower war criminals at the expense of Yemenis, & undermine opportunities to build genuine & sustainable peace.”

Ryan reported from Washington.