For the past few years, officials in Washington and their counterparts in Riyadh and Abu Dhabi have justified the ongoing war effort in Yemen in simple terms. For the interests of the region, it was vital to push back Yemen's Houthi rebels and curb the influence of their Iranian backers.
No matter the mounting civilian body count and the devastating humanitarian toll of the conflict, the need to bash Tehran in this part of the world remained paramount. In United States President Donald Trump's view, the Saudi-led fight was so urgent a cause that it justified overriding congressional opposition to US arms sales to the two wealthy kingdoms.
But things were never that simple. The war in Yemen takes place over a fractured political landscape marked by long-standing turf wars, tribal enmities and opportunistic factions seeking to expand their fiefdoms. That complexity was on display this past weekend as the Saudi-led coalition targeted its own allies — southern separatists backed by the United Arab Emirates — in a pitched battle over the strategic port city of Aden. The separatists, angry at other factions within the Saudi-led coalition, seized government buildings and held on to them despite Saudi airstrikes.
According to United Nations officials, at least 40 people were killed and 260 injured in four days of clashes that fell around the commemoration of Eid al-Adha, one of the holiest dates in the Muslim calendar.
"It is heartbreaking that during Eid al-Adha families are mourning the death of their loved ones instead of celebrating together in peace," Lise Grande, the top UN humanitarian official in Yemen, said. "Our main concern right now is to dispatch medical teams to rescue the injured. We are also very worried by reports that civilians trapped in their homes are running out of food and water."
Though the fighting quieted down, there's a lingering uncertainty over the future of the Saudi-Emirati alliance.
"It is quiet now, but people are still worried. We don't know where matters are heading," Adel Mohammed, an Aden resident, told Reuters on Tuesday.
On the same day, in a bid to calm tensions, official social media accounts in both Saudi Arabia and the UAE publicised meetings between Saudi King Salman, Crown Prince Mohammed bin Salman and the UAE's de facto ruler, Mohammed bin Zayed. But clear divisions are getting harder to ignore.
"This weakens the coalition by exposing undeniable cracks beneath the surface," Elisabeth Kendall, a Yemen scholar at Oxford University's Pembroke College, told the Washington Post.
"It is becoming increasingly obvious that the UAE and Saudi Arabia do not share the same end goals in Yemen, even though they share the same overarching goal of pushing back the perceived influence of Iran."
There's little new about the secessionist ambitions in Aden or the south of Yemen, but it seems that Emirati support — in particular, military training — has bolstered the cause of the separatists, who have long wanted to split from the country's more populous north.
As the Washington Post explained this week, the separatists, and the UAE, also disapprove of Yemeni President Abed Rabbo Mansour Hadi's alliance with Islah, an influential Islamist party.
Although the Saudis consider Islah vital for rebuilding Yemen, the UAE is opposed to any significant role for Islah because of its ties to the Muslim Brotherhood, a regional political Islamist movement that the Emirati leadership views as a domestic threat, as well as a malign and radical force in the Arab world.
The Saudis have been doggedly committed to combating the Houthis on their southern border and returning the weak Yemeni Government to the capital, Sanaa, but the Emiratis are less invested in backing Hadi and have other interests in play. The Persian Gulf kingdom once tagged by former US Defence Secretary Jim Mattis as "Little Sparta" — presumably for its surprising military prowess rather than its dependence on poorly treated labourers — is entangled in a geopolitical rivalry with Qatar and Turkey that has flared in disparate proxy conflicts from Libya to Somalia.
"The Emiratis are trying to place themselves as some sort of hegemon in the Horn of Africa," Fatima Alasrar, a Yemen expert and non-resident scholar at the Middle East Institute, said, pointing to Emirati concerns over the Bab al-Mandeb Strait and the island of Socotra.
And then there's the matter of Iran. As Trump has increased pressure on the regime in Tehran in recent months, the UAE has played a conspicuously circumspect role. It resisted the urge to directly blame Iranian forces for sabotage attacks on shipping vessels in the Persian Gulf in recent months and recently sent a delegation of naval officials to meet Iranian counterparts in a bid to help de-escalate a budding regional crisis.
Analysts suggest that an explosion of hostilities would be particularly painful for the UAE, a financial and tourist hub in the region.
And the unpredictability and occasional brazenness of Trump and the Saudi crown prince may have persuaded the Emirati leadership to embark on a different course.
"The stakes for the UAE are stupendously high.
"An attack that hit Emirati soil or damaged their critical infrastructure would be devastating," Elizabeth Dickinson of the International Crisis Group told the Washington Post.
"It would symbolically compromise the reputation of one of the region's most economically dynamic countries."
Those concerns also probably shadowed the UAE's announcement that it would steadily withdraw its forces from Yemen.
"The impression in Israel is that the UAE does indeed want to halt its involvement in the war in Yemen," reported Haaretz's Amos Harel last week.
"The Houthis have already announced that they will stop attacking UAE targets in response to its change of policy. It now appears that Saudi Arabia will be left to fight in Yemen alone, with the help of a few units of mercenaries it managed to recruit from various countries, including Sudan."
The UAE didn't have a very significant footprint of its own troops on the ground in Yemen, but the militias it supported and trained were on the frontlines of the campaigns against the Houthis.
"The drawdown is more symbolic in the way that it sends a message of goodwill to Iran and the Houthis," Alasrar said.
Implicit in that message may be another admission: that the full-frontal campaign against Iran and its regional proxies could be waged more delicately than it has been.
"It looks like it was overreach, and they didn't calculate the consequences," a Dubai businessman told the Washington Post.