The Hunt for ISIS Pivots to Remaining Pockets in Syria

AL UDEID AIR BASE, Qatar — Secretive drones and surveillance jets are boring down on an estimated 3,000 remaining Islamic State fighters, who are hiding in Syria along a short stretch of the Euphrates River and surrounding deserts, as the American military campaign against the extremist group enters its final phase.

But the focus on a 15-square-mile enclave near the Iraqi border is complicated by skies congested with Russian, Syrian and Iranian aircraft as rival forces converge on that last main pocket of Islamic State militants in Syria.

“It drives up the complexity of the problem,” Lt. Gen. Jeffrey L. Harrigian, the air commander for Syria and Iraq, said of the increasingly risky airspace and near collisions, in an interview at his headquarters at this sprawling air base outside Doha, the capital of this tiny Persian Gulf nation.

With names like Joint Stars and Rivet Joint, the American spy planes are trying to track the last Islamic State fighters and top leaders, eavesdrop on their furtive conversations, and steer attack jets and ground forces to kill or capture them.

The three-year American campaign has largely achieved its goal of reclaiming territory in Syria and Iraq, and the Islamic State’s religious state, or caliphate, appears all but gone. Still, senior military commanders and counterterrorism specialists caution that the organization remains a dangerously resilient force in Iraq and Syria, and a potent global movement through its call to arms to followers on social media.

“As they lose the caliphate’s physical terrain, they’ll adapt guerrilla tactics,” Gen. Joseph L. Votel, the head of United States Central Command, which oversees operations in the Middle East, said in an interview during a regional security conference in Bahrain. “ISIS has been beat up pretty bad. But this is a different kind of organization so we don’t know what they might try to add. They’ve been very adaptive.”

Echoing earlier comments by Defense Secretary Jim Mattis, General Votel said American forces will remain in eastern Syria, alongside their Syrian Kurdish and Arab allies, as long as needed to defeat the Islamic State, also known as ISIS or Daesh. “What we don’t want to do is leave a mess,” General Votel said, something “worse than what we found.”

Here at Al Udeid, home to some 10,000 American and other allied troops, commanders are running the air wars not only in Iraq and Syria, but also the campaign in Afghanistan that is expected to increase sharply in the coming months under President Trump’s more aggressive strategy for combating the Taliban, ISIS and other extremist groups there.

For now, though, the bulk of the 300 combat aircraft under General Harrigian’s command are concentrating on the Islamic State. “Job One still is to get to the military defeat of ISIS,” General Harrigian said. “We need to make sure we stay focused on that.”

At the peak of its power three years ago, the Islamic State controlled a swath of territory in Syria and Iraq as big as Kentucky. Now that area has dwindled to half the size of Manhattan, and is shrinking fast.

The hunt for the final Islamic State fighters and operatives draws on an aerial armada of combat aircraft based in Jordan, Turkey and several Persian Gulf countries, as well as the aircraft carrier Theodore Roosevelt, newly arrived in the Persian Gulf.

Warplanes are working with Syrian Kurdish and Arab militia on the ground to track down ISIS fighters, some of whom have disappeared in Sunni enclaves along the Euphrates River near the Iraq-Syria border. Others have made a dash across deserts west — through Syrian army lines — and south into Iraq’s Anbar Province to avoid capture, or worse.

The United States has doubled the bounty, to $25 million, for information leading to the death or capture of the elusive leader of the Islamic State, Abu Bakr al-Baghdadi.

Russia and the United States back separate ground offensives against the Islamic State in eastern Syria, both of which are advancing in the oil-rich Deir al-Zour Province bordering Iraq.

The assaults are converging on Islamic State holdouts from opposite sides of the Euphrates, which bisects the province. Syrian Army troops backed by Russian air power and Iranian militia are advancing along the western side of the river; Syrian Arab and Kurdish fighters, supported by American warplanes and Special Operations advisers, are pushing along the eastern river banks.

American Reaper drones armed with intelligence collected from U-2 and other spy planes are hunting ISIS fighters, alongside Air Force and Navy fighter-bombers. A-10 attack planes, armed with laser-guided rockets and a 30-millimeter cannon, have provided effective air cover for advancing Syrian Kurdish and Arab militias.

Other American warplanes have dropped 500-pound and 250-pound bombs, often timed to detonate split seconds after impact to minimize civilian casualties, air planners said.

“We’re piling up a lot of airplanes in a very small piece of sky,” said Col. Jeff Hogan, deputy commander of the air operations center at Al Udeid. He said the concentration of unarmed reconnaissance planes, armed fighters and attack planes — all warily eyeing Russian and Syrian jets nearby — were converging over Abu Kamal and Al Qaim, towns just across from each other on the Syrian and Iraqi borders.

At the height of the air campaign in Raqqa, Syria, over the summer, American and allied warplanes dropped nearly 200 bombs and missiles each day on Islamic State targets. Now, the warplanes are stalking their prey more selectively, dropping one-tenth of that over a weekend — and sometimes less, said military officials at Al Udeid.

“We’re focused very hard on not letting ISIS escape,” said Colonel Hogan, 44, from Olympia, Wash. “We’ve got to annihilate them.”

Sometimes the bombs find high-ranking targets. Abu Faysal, a senior Islamic State leader, and his deputy, Abu Qudamah al-Iraqi, were killed in a Dec. 1 airstrike in the Middle Euphrates River region, the Central Command said in a statement.

Others have slipped away, across the border into Turkey or in a mad dash through Syrian army lines and desert to areas south of Damascus, the Syrian capital, Col. Ryan Dillon, a military spokesman in Baghdad, said last week.

“As the caliphate is squeezed, these remaining fighters would bleed off into surrounding countryside and Sunni strongholds,” said Nicholas J. Rasmussen, who last week stepped down as head of the National Counterterrorism Center.

Mr. Rasmussen warned that even with its leaders on the run, the Islamic State, also known as ISIS or Daesh, remains a deadly worldwide force still capable of directing, enabling and inspiring terrorist attacks.

“We continue to see key individuals with a focus on external operations trying to advance plotting and planning both locally and abroad,” Mr. Rasmussen, who served as the country’s top counterterrorism official for three years, said in an interview. “Now, more often what we worry about are threats that emerge from individuals acting on their own, not waiting for guidance.”

That would include the suspects who carried out the recent terrorist attacks in Lower Manhattan and the New York City subway. Even as the Islamic State loses ground in Iraq and Syria, its affiliates in Libya, West Africa, the Philippines, and Sinai, remain persistent threats and have even attracted some new fighters, despite suffering setbacks in recent months.

“ISIS became a brand,” Brett McGurk, the special American envoy for the global coalition to defeat the extremist group, said last week in Washington. “This is going to go on for some time.”