A deadly attack late last week on soldiers from oil-rich Gulf states deployed in Yemen as part of a Saudi-led coalition fighting the country's Shiite rebels may well have been designed to break the coalition's will. If that was the aim, it backfired.

Instead, the killing of dozens of troops — most of them from the United Arab Emirates — has upended much of the ambiguity about the U.S.-backed coalition's boots-on-the-ground role in Yemen and is prompting the alliance to intensify what has effectively become a proxy war against Iran.

In the eyes of many across the Sunni-ruled Gulf states, Yemen — with its Iranian-backed Houthis — has become a key battleground in a Middle Eastern twist on the Cold War domino theory: if Iran cannot be checked in Yemen, the thinking goes, it could ramp up the pressure in Shiite-majority Bahrain and elsewhere in the region.

The missile assault on Friday struck an ammunition depot in the Yemeni province of Marib, about 120 kilometers (75 miles) east of the capital, Sanaa.

Hardest hit in the attack was the UAE, a federation of seven states that includes Dubai and the oil-rich capital, Abu Dhabi, which lost 45 soldiers. Ten Saudis were killed in the blast too. Bahrain also lost five soldiers, though it was not clear if they were killed in the same incident.

Emirati fighter planes have responded to the attack by pounding positions and arms caches used by Iranian-backed Shiite rebels known as Houthis — rebels that the Gulf states see as little more than tools of Tehran. Iran supports the Houthis politically but denies arming them.

The Gulf nation of Qatar significantly ramped up its involvement in the conflict on Monday, deploying about 1,000 ground troops backed by armored vehicles and Apache helicopters, according to Yemeni officials and the Qatar-based Al Jazeera television. Qatar neither confirmed nor denied its role.

"Our armed forces ... are more resolved and determined to liberate Yemen and flush out the scum after the tragic incident," Sheikh Mohammed bin Zayed Al Nahyan, the powerful Abu Dhabi crown prince and deputy supreme commander of the UAE armed forces, assured visiting Yemeni President Abed Rabbo Mansour Hadi after the attack.

Radio stations across the UAE have replaced their usual upbeat fare with Quranic recitations and classical music to mark three days of mourning commemorating the unprecedented war loss — an honor typically reserved for the country's top leaders.

Sheikh Mohammed and other top government officials visited families of killed soldiers. Outside medical clinics, Emirati men in traditional white garments known as thobes have been lining up to give blood for those still recovering from the attack.

The managing editor of the widely read UAE daily Gulf News, Mohammed Almezel, suggested in an op-ed that the deaths were a "Pearl Harbor moment" that will strengthen the Emirates' determination in Yemen. He described the fight as "part of a strategic decision to defend and preserve the security and stability of the Gulf strategic hemisphere."

"The cowardly attack in Marib will not intimidate the Arab coalition into abdicating its responsibility of defending justice and supporting the right of the Yemeni people," he wrote.

Mustafa Alani, the director of the security and defense department at the Gulf Research Center in Geneva, said that rather than spooking it, Friday's attack will likely prod the coalition to "finish the job in Yemen under any circumstance."

Many in Gulf states such as Saudi Arabia and the Emirates support the war and will likely continue to do so despite the casualties, as a way to check what they see as Iran's expansionist policies in the region, Alani said.

"This is not a battle for Yemen," Alani said. "The great majority of the population understands it's much wider than that. It's a strategic confrontation, and they are ready to sacrifice."

"It is a matter of survival in the region," Alani added.

That sentiment was echoed by businessman Abdullah al-Musa outside a Dubai mosque. He described the fight in Yemen as a way to ultimately help the Emirates.

"They are our neighbors. If there is a problem in your neighbor's house, tomorrow it will be in your house," he said.

The U.S.-backed coalition has been carrying out airstrikes since March in a bid to halt the Houthi rebel power grab that captured Sanaa and areas in the country's north last year. The push forced Hadi and his government into exile in Saudi Arabia, and for a while the rebels held the strategic southern port city of Aden until pro-government forces pushed the rebels out.

The fighting in Yemen, the Arab world's poorest country, has killed more than 2,100 civilians, according to figures from the United Nations.

The Gulf states had maintained a policy of ambiguity about their role on the ground even as it became clearer that they were deploying troops and hardware.

Alani, who has close ties to Saudi officials, said the Gulf troops inside Yemen include special forces soldiers and airpower support specialists, as well as armored units that arrived more recently.

The bulk of the fighting on the ground is being done by Yemenis, including infantry soldiers trained inside Saudi Arabia, he said. Alani predicted the Gulf coalition would pump more soldiers and equipment into the country in the wake of Friday's attack.

The UAE is a major buyer of military hardware and has increasingly deployed troops on military and humanitarian missions abroad. It last year began requiring compulsory military service for adult males, and it is one of the most prominent Arab members of the U.S.-led aerial campaign against Islamic State militants in Iraq and Syria.

At least five other members of the Emirati military have been killed in Yemen this year, and another died during training exercises related to the operation in Saudi Arabia.

Theodore Karasik, a Dubai-based geopolitical analyst, agreed that Friday's attack is unlikely to deter the Emirates.

"Yemen is part of the strategic calculation of the UAE," he said, citing Emirati concerns not just about close ally Saudi Arabia's security but also about freedom of navigation in the Red Sea and the Gulf of Aden off Yemen's shores.

The Emirates relies heavily on international trade and Dubai's government-backed DP World is one of the world's largest seaport operators. The country is also a major backer of Egyptian President Abdel-Fattah el-Sissi, whose country's Suez Canal depends on open sea lanes in the Red Sea.

A somber scene Saturday perhaps best reflected UAE's resolve over Yemen — the coffins of the fallen Emirati soldiers were brought home by plane to the Al Bateen Airport in Abu Dhabi. The caskets, each draped in the Emirati flag, were then carried down a red carpet as an honor guard stood by on the tarmac.

The soldiers' final return is since being replayed on state-owned television, along with patriotic file footage of Emirati troops and fighter planes in action.

___

Follow Adam Schreck on Twitter at www.twitter.com/adamschreck .