AL UDEID AIR BASE, Qatar — As the United States prepares to intensify airstrikes against the Islamic State in Syria, the Arab allies who with great fanfare sent warplanes on the initial missions there a year ago have largely vanished from the campaign.
The Obama administration heralded the Arab air forces flying side by side with U.S. fighter jets in the campaign's early days as an important show of solidarity against the Islamic State, also known as ISIS or Daesh. Top commanders like Gen. Lloyd J. Austin III, who oversees operations in Syria and Iraq, still laud the Arab countries' contributions to the fight. But as the United States enters a critical phase of the war in Syria, ordering Special Operations troops to support rebel forces and sending two dozen attack planes to Turkey, the air campaign has evolved into a largely U.S. effort.
Administration officials had sought to avoid the appearance of another U.S.-dominated war, even as most leaders in the Persian Gulf seem more preoccupied with supporting rebels fighting the government of President Bashar Assad of Syria. Now, some of those officials note with resignation, the Arab partners have quietly left the United States to run the bulk of the air war in Syria — not the first time Washington has found allies wanting.
Saudi Arabia and the United Arab Emirates have shifted most of their aircraft to their fight against Iranian-backed Houthi rebels in Yemen. Jordan, reacting to the grisly execution of one of its pilots by the Islamic State, and in a show of solidarity with the Saudis, has also diverted combat flights to Yemen. Jets from Bahrain last struck targets in Syria in February, coalition officials said. Qatar is flying patrols over Syria, but its role has been modest.
"They've all been busy doing other things, Yemen being the primary draw," Lt. Gen. Charles Q. Brown Jr., who leads the air war from a $60 million command center at this sprawling base in Qatar, said of the Arab allies, who he said still fly periodic missions in Syria and allow U.S. jets to use their bases.
The United Arab Emirates last carried out strikes in Syria in March; Jordan in August; and Saudi Arabia in September, according to information provided by allied officials last week. But the Arab allies insist they are still playing an essential, if less active, military role in the war.
"Jordan's commitment to this fight is unwavering," said Dana Zureikat Daoud, a spokeswoman for the Jordanian Embassy in Washington. "We remain an active partner and contributor to the international coalition, and continue to conduct airstrikes against Daesh targets."
The engagement of Western allies, like France and Australia, has also been limited. They have conducted a smattering of strikes in Syria, but have reserved most of their firepower for Islamic State targets in Iraq. Canada's new prime minister, Justin Trudeau, has promised to fulfill his campaign pledge to end Ottawa's role in the air campaign altogether. And none of the Western allies appear eager to join the United State in basing warplanes at Incirlik air base in Turkey, a move that would make it easier to increase strikes against militants in northern Syria and Iraq.
So far, eight Arab and Western allies have conducted about 5 percent of the 2,700 airstrikes in Syria, compared with 30 percent of the 5,100 strikes in Iraq, where many NATO partners also fly missions against the Islamic State. But the United States was always likely to fly the majority of the missions in Syria, as it does in Iraq, since its air forces are much larger than those of the Arab states or any forces deployed by Western allies.
Defense Secretary Ash Carter has promised Congress that the air war in Syria will escalate "with a higher and heavier rate of strikes," including more attacks against top Islamic State leaders and oil fields that remain one of the group's main financial lifelines. But the revamped effort is already facing challenges.
For the first time since 2007, the United States does not have an aircraft carrier in the Persian Gulf and will not again until mid-December; the Navy needed time to conduct badly needed repairs on its fleet. The aircraft carrier Theodore Roosevelt and its air wing, responsible for about 10 percent of the daily strikes in Iraq and Syria, left the gulf in early October. France said Thursday that it would send its only aircraft carrier to the gulf to help fill the gap.
Brown said the coalition could also pick up the slack using land-based U.S. and allied warplanes, including a dozen A-10 ground-attack planes newly deployed to Incirlik air base and a dozen F-15's on their way there.
Incirlik is far more convenient to the fight — 15 minutes flight time to the Syrian border compared with nearly five hours from Persian Gulf bases — making it easier to increase the number of planes that can spend more time hunting Islamic State targets. But Australia and most of the European allies are reluctant to leave their bases in the Middle East, despite the shorter flight times.
"It's not just as simple as, 'go to Turkey,'" Gen. John R. Allen, the special U.S. envoy to the coalition fighting the Islamic State, told Congress last month. "They've got bilateral relationships in the gulf that are old and have been cultivated in order for them to deploy."
So while France will still conduct airstrikes in Syria — it has carried out about 270 strikes in Iraq and Syria overall, though only two so far in eastern Syria, a senior French official said — it will continue to fly out of Jordan and the United Arab Emirates, at least for now. The Australians will continue F/A-18 combat missions over Syria that began on Sept. 11, expanding beyond strikes in Iraq. But they, too, do not want to give up their base in the United Arab Emirates.
Britain has talked tough about going after the Islamic State, but unlike France, its actions have not matched its talk. Britain currently flies bombing missions over Iraq and intelligence, surveillance and reconnaissance flights over Syria.
The British defense and foreign secretaries have said they want forces to be able to fight the Islamic State in Syria as well as in Iraq, and that it is absurd to stop planes at a border that the militant group does not recognize, especially since its command centers are in Syria. But stung by Britain's experiences in Iraq and Afghanistan in support of U.S. wars, Prime Minister David Cameron has promised to seek the approval of Parliament before taking any military action in Syria. He has said he will only press for such a vote if he has "a clear majority" in favor, and so far he has failed to find one.
The recent election of the hard-left Jeremy Corbyn as the leader of the Labour Party and Russia's military intervention in Syria have made it even less likely that Cameron will call for a vote.
While some Iraqi and Western experts have criticized the pace of the air campaign, Brown described two broad areas where he expected attacks against the Islamic State to increase in the coming days. First, he said, newly armed Syrian Kurdish and Arab fighters would put pressure on Islamic State fighters in and around Raqqa, the group's self-proclaimed capital, forcing them to move from their defensive positions.
"When they are active and moving, that increases our activity for strikes," Brown said. "Daesh presents itself as a target more."
This is what happened in July, when a Kurdish offensive in northeastern Syria yielded about a dozen strikes a day. But some Kurdish fighters ran low on ammunition, bad weather set in at times, and U.S. commanders focused on targets in western Iraq, reducing strikes in Syria last month to just four a day.
The general said the campaign would also intensify attacks on a second set of targets — fixed sites such as oil-production facilities, bomb-making factories and other so-called critical nodes that support the Islamic State's war effort.
Shifting more reconnaissance and surveillance planes to Incirlik to linger over targets longer will also help. Last month, U.S. forces dropped bombs on 67 percent of their strike missions, up from about 25 percent a year ago — a sign there are more targets to hit.
"What I want to have," Brown said, "is a steady of set of strikes that keeps the pressure on Daesh."
Eric Schmitt reported from Qatar and Michael R. Gordon from Irbil, Iraq. Steven Erlanger contributed reporting from London.