On a visit to Oman this month, US defence secretary James Mattis called US-UAE joint counter-terrorism operations against Al Qaeda in Yemen a model for American troops being present in the war-ravaged country.
He then cited the battle to recapture the southern port of Mukalla, which had been held by Al Qaeda in the Arabian Peninsula. "The United Arab Emirates, with some American help — intelligence help principally, had gone in, organised the local tribes to take it away and Mukalla Port fell in 36 hours after being held for a year. And so we're there to help that sort of an effort," Mr Mattis said.
Mukalla was recaptured in April, 2016. US-UAE efforts against Aqap have since intensified, liberating Shabwa recently, Abyan, Ahwar, and other towns around Hadramawt province. Experts who spoke to The National credited military effectiveness, strategic alignment and local elements, behind the strengthened US-UAE bond in the war.
For the US, Yemen’s strategic importance is its geographical location "on one of the busiest highways for international maritime trade in the entire world", said Nicholas Heras, a senior fellow at the Centre for New American Security in Washington, where he focuses on Yemen issues.
"Whatever instability that occurs in Yemen has the potential to threaten or jam up vital global trade routes."
The importance of Yemen to the US also lies in the recent past.
"Al Qaeda's strongest local branch is located in Yemen and has used this position to plan attacks against the US," Mr Heras said.
The attack on the USS Cole destroyer in 2000, the attempt of shoe bomber Richard Reid on an American Airlines flight in 2001, the attack on the US embassy in Sanaa in 2008, and the foiled ink cartridges plot in 2010 are examples of Aqap's threat to American interests.
While the Pentagon only admits to "a small number" of American troops being in Yemen, Mr Heras considers the US military to be "deeply involved in the Yemen conflict, in ways that would surprise the American people".
"It is not overstating it to say that Yemen is the hottest war being fought by US soldiers in the Middle East that Americans have never heard about," he said.
Mr Mattis last week successfully urged Congress to block a bill that would have required any American forces not involved in fighting Al Qaeda in Yemen to leave the country within 30 days.
_______________
Read more: UAE-backed campaign puts Al Qaeda under pressure in Yemen
_______________
But when it comes to fighting Aqap and ISIL in Yemen, the level of US-UAE co-operation is now so close that the US military "has agreed to conduct joint kinetic operations with Emirati forces", according to Mr Heras. That's something "American generals only sign off on for the most competent partner militaries", such as Nato, he said.
John Arterbury, a Yemen analyst at the Navanti Group, a research and analysis company, told The National that the narrow focus of the US mission in Yemen is "fighting Aqap and ISIL, while also pushing for a halt to the civil war and an increase in aid" has helped its success.
"Aqap is on the back foot. UAE-backed local forces have systematically driven the group from towns and cities, and are now pursuing it into more remote areas across south Yemen," Mr Arterbury said, "securing rural valleys over the past month in Hadramawt and Shabwa provinces being prime examples of this."
The US sees the UAE as a state with capable armed forces and an abiding interest in southern Yemen, Mr Arterbury said. "These complementary aims and abilities make the US and UAE natural partners in regards to pursuing counter-terrorism efforts in the country’s south."
On the ground "the UAE works with tribes and other local networks, providing lucrative incentives to collaborate against Aqap".
Mr Arterbury cautioned however, that any involvement in southern Yemen must also take into consideration the powerful bloc favouring southern secession, which "will be a tricky feat for any state involved in Yemen going forward”.
One area where the UAE and the US differ is on targeting of the Houthis. While the US is active "especially at Bab Al Mandeb, to support the mission of interdicting Iranian supplies to the Houthis", it does not directly target the fighters in the conflict, argued both experts.
This month, however, US Gen Robert Ashley, director of the Defence Intelligence Agency, warned of the Houthis' increased naval threat. He said their new capabilities include "anti-ship missiles, explosive-laden boats, and mines", making the Yemen war a "threat to vital international shipping lanes through the Red Sea".
The long-term challenge of ending the war will be the most daunting in Yemen. While the "US-UAE backed efforts have proven relatively successful so far in displacing Aqap, the real challenge will come in a post-conflict setting" in sustaining the effort, and maintaining the close-knit coalitions, said Mr Arterbury.