A brazen territorial grab by
Al Qaeda in the Arabian Peninsula, which was long forced into the shadows by U.S. drone strikes and commando raids, has taken advantage of the growing chaos in Yemen's multi-sided war to carve out a potential haven that counter-terrorism experts say could help it launch terrorist attacks.
After seizing a regional airport and a coastal oil terminal this week, Al Qaeda militants consolidated their gains Friday in Mukalla, an Arabian Sea port. Fighters stormed a weapons depot and seized armored vehicles and rockets after apparently forging a truce with local tribes and forcing government troops to flee.
Many of the armories in Yemen hold weapons and ammunition that the U.S. helped supply to support government counter-terrorism operations against AQAP, as the Al Qaeda franchise is known.
AQAP has repeatedly attempted to smuggle sophisticated bombs onto passenger jets and cargo planes headed for the United States. U.S. intelligence considers it the terrorist network's most active and most dangerous franchise and says it has a global strategy.
But Islamic State's dramatic claim to control a vast caliphate, its ability to raise huge sums of cash from oil exports and other schemes, its stunning early successes on the battlefield, and its Internet-driven appeals to zealots around the globe have eclipsed Al Qaeda's once-fierce image.
Islamic State has "changed the game" for terrorist groups, Bruce Hoffman, a terrorism expert at Georgetown University, said in an interview.
It's been said that publicity provides oxygen to terrorist groups. But now, Hoffman said, "territory and safe havens" provide it for them.
AQAP suddenly has "a lot more elbow room," said Stephen Seche, the U.S. ambassador to Yemen from 2007 to 2010.
"If they can seize and hold territory … if they can loot banks, they are seen as more viable and can recruit troops," he said.
The fighting in Yemen has hobbled a long-established U.S. counter-terrorism operation, forcing a special operations unit and intelligence officials to destroy equipment and abandon the country last month.
"Our efforts have to change their character but remain steady in their intensity," he said.
Even amid the chaos, a drone strike this week in the southern province of Shabwa reportedly killed a senior cleric who had acted as AQAP's spokesman.
Yemen has been engulfed in conflict since last fall, when a Shiite Muslim minority group called the Houthis overran the capital city, Sana, and took over much of the government.
The Houthis then pushed south and appeared on the verge of capturing Aden, the country's economic hub, when Saudi-led warplanes launched a fierce counterattack on March 26 that continues today. The rebel onslaught forced Yemen's president, Abdu Rabu Mansour Hadi, to flee the country.
The Houthis have fought with AQAP, Sunni Muslims whom they consider enemies. But the Saudi airstrikes have only targeted the Houthis — giving Al Qaeda a relatively free hand.
They "are doing exactly what we expected them to do, which is take advantage of the chaos," a U.S. counter-terrorism official said Friday. The pressure on them has been "greatly reduced," he said, speaking on the condition of anonymity to describe internal assessments.
AQAP has captured territory before. In 2011, the group took advantage of political turmoil sparked by anti-government protests to seize several cities in Yemen's south and east. In mid-2012, military forces and local tribes loyal to Hadi's government in Sana pushed them back into a rugged eastern enclave.
"They get out of control when the cage door opens," the U.S. official said.
Thick plumes of smoke rose Friday over Sana as some of the heaviest bombing in weeks shook the capital, including residential areas. Major streets were deserted as hundreds of families fled the city.
The United Nations reported that at least 150,000 people have been displaced by the conflict. It said more than 750 civilians have been killed since mid-March.
"Thousands … have now fled their homes," Johannes van der Klaauw, the U.N.'s humanitarian coordinator for Yemen, said in a statement. "Ordinary families are struggling to access healthcare, water, food and fuel — basic requirements for their survival."
President Obama spoke by phone Friday with Saudi Arabia's King Salman. The White House said the two agreed that the collective goal is "to achieve lasting stability" in Yemen through a negotiated political solution and "discussed the importance" of the humanitarian crisis.
Aden now appears in ruins, pummeled by airstrikes and ravaged by close-quarters street fighting. Aid groups report overflowing morgues and growing shortages of everything from food to electricity. A few shipments of medical supplies have arrived, far outstripped by needs.
With the Saudis focused on the Houthis, AQAP fighters launched a jailbreak near Mukalla that freed about 300 prisoners, including several dozen of their comrades, officials and residents said.
The militants also stole more than $1 million in Yemeni rials from the local branch of the Central Bank, security officials said, and set up roadblocks across the city.
Col. Patrick Ryder, spokesman for U.S. Central Command, which oversees military forces in the Middle East, said AQAP posed "a significant threat" even before it captured Mukalla.
"We continue to keep capabilities in the region to address that," he told reporters at the Pentagon.
AQAP has a unique reputation among U.S. counter-terrorism officials.
They say the group's top bomb maker, Saudi-born Ibrahim Hassan Asiri, assembled the underwear bomb that Nigerian-born Umar Farouk Abdulmutallab tried to detonate on a Northwest Airlines flight over Detroit in December 2009.
Asiri also allegedly hid bombs in printer cartridges that were meant to detonate in cargo planes over U.S. cities in 2010. The devices were intercepted after a tip from Saudi intelligence.
In 2013, a threat linked to AQAP prompted U.S. officials to close more than two dozen embassies and consulates around the world. This year, the group said it had planned the deadly rampage in January at the Paris offices of the satirical magazine Charlie Hebdo.
Dzhokhar Tsarnaev was convicted of terrorism-related crimes in a federal court in Boston last week. His older brother was killed in a shoot-out with police several days after the bombing.