WASHINGTON — They are taking on a larger combat role in Afghanistan, where the war was supposed to be over. They are headed to Syria to help fight the Islamic State in its stronghold. And President Barack Obama recently ordered nearly 300 of them to Cameroon to assist African troops in their battle against a militant group that has pledged loyalty to the Islamic State.

With the Middle East in tumult, radical groups holding swaths of territory in Africa, and a presidential campaign fanning fears of a growing terrorism threat, the White House has steadily expanded the global missions of U.S. special operations troops.

Even as Obama has repeatedly said that he opposes American "boots on the ground" in far-flung parts of the world, his administration continues to carve out exceptions for special operations forces — with U.S. officials often resorting to linguistic contortions to mask the forces' combat role.

The Obama administration long ago showed its inclination to rely on special operations troops and clandestine missions as an alternative to large wars of occupation. But the spread of the Islamic State over the past year — from its hubs in Syria and Iraq to affiliates in Africa and South Asia — has led the White House to turn to elite troops to try to snuff out crises in numerous locations.

These deployments, as well as other missions being considered, have upended the Obama administration's goal of withdrawing from countries that for more than a decade have been crucibles of combat for the U.S. military.

The White House is now considering a Pentagon proposal to maintain at least one base in Afghanistan for years to come, according to U.S. military officials. Senior officials spoke to the New York Times about issues related to special operations forces only on the condition of anonymity because most of the specifics of their missions are classified.

This plan would run counter to Obama's original pledge to remove all troops from Afghanistan except for a counterterrorism force and the troops guarding the U.S. Embassy in Kabul. Obama revised his withdrawal plans in October, saying that about 5,500 troops would remain in the country through the end of his term in early 2017.

The proposal would use that Afghanistan base as a hub for special operations troops and intelligence operatives throughout Central and South Asia, part of a larger network of bases the Pentagon is envisioning in part to tackle ISIS and its more than half-dozen affiliates in countries like Libya, Egypt and Yemen.

During the peak of the wars in Iraq and Afghanistan, nearly 13,000 special operations forces were deployed on missions across the globe, but a large majority was assigned to those two countries. Now, roughly half of the 7,500 elite troops overseas are posted outside the Middle East or South Asia, operating in 85 countries, according to the U.S. Special Operations Command based at MacDill Air Force Base in Tampa.

There is other, subtler, evidence of the sway of senior special operations officers. When Obama appeared before reporters in the Pentagon briefing room this month to discuss his administration's strategy for fighting ISIS in Syria, he was flanked by a coterie of top national security officials, including Vice President Joe Biden, Defense Secretary Ash Carter and Gen. Joseph Dunford Jr., the chairman of the Joint Chiefs of Staff.

Standing beside them was Gen. Joseph Votel, the head of the U.S. Special Operations Command, whose presence raised eyebrows at the Pentagon.

The threat from ISIS has become more prominent in the presidential campaign since the attacks in Paris and San Bernardino, Calif., and many candidates have proclaimed a need for more special operations troops to be deployed far and wide. Sen. Marco Rubio, R-Fla., has talked about embedding special operations troops with Iraqi soldiers on the front lines, and Hillary Clinton said she would consider sending more special operators to Syria than the 50 that Obama recently authorized to assist rebels fighting ISIS.

These calls for more U.S. special operations troops have come even as some of the same candidates said they opposed boots on the ground in places such as Syria. Obama himself tried to draw a distinction during an interview this month with CBS News, when a reporter asked if recent special operations deployments in Iraq and Syria meant that he was reversing his pledge.

"You know, when I said, 'No boots on the ground,' I think the American people understood generally that we're not going to do an Iraq-style invasion of Iraq or Syria with battalions that are moving across the desert," he said.

But in a Dec. 2 conference call with reporters, Col. Steven Warren, a military spokesman in Baghdad, said, "I mean, a raid is a combat operation. There is no way around that. So, yeah, more Americans will be coming here to Iraq, and some of them will be conducting raids inside of both Iraq and Syria."

Critics say using special operations troops this way is a half-step.

"The problem is that the expeditionary targeting force can easily become a waste of U.S. blood and money," Anthony Cordesman, a senior analyst with the Center for Strategic and International Studies, wrote recently. "The Obama administration reacts to every new problem with ISIS by making a limited increase in military force that is too little and too late."

The same criticism has been leveled at the administration's decision to send up to 50 special operations forces to advise and assist rebels against ISIS in eastern Syria.

The White House also is relying on special operations troops elsewhere. About half of the 3,500 U.S. forces in Afghanistan are special operators and have recently fought pitched battles in Helmand province against the Taliban.

Obama in October announced that he had ordered 300 troops, most of them special operators, to Cameroon to work with soldiers from Cameroon, Chad, Benin, Niger and Nigeria to counter the Nigeria extremist group Boko Haram. The troops will not engage in combat, he said.