That concern gives weight to arguments for greater reliance on special operators as the Trump administration for now eschews larger deployments of conventional troops and proposes deep cuts in foreign aid and State Department budgets.
The global reach of special operators is widening. During the peak of the conflicts in Iraq and Afghanistan, nearly 13,000 Special Operations forces were deployed on missions across the globe, but a large majority were assigned to those two countries. Now, more than half of the 8,600 elite troops overseas are posted outside the Middle East or South Asia, operating in 97 countries, according to the Special Operations Command.
Still, about one-third of the 6,000 American troops currently in Iraq and Syria are special operators, many of whom are advising local troops and militias on the front lines. About a quarter of the 8,400 American troops in Afghanistan are special operators.
In Africa, about one-third of the nearly 6,000 overall troops are Special Operations forces. The only permanent American installation on the continent is Camp Lemonnier, a sprawling base of 4,000 United States service members and civilians in Djibouti that serves as a hub for counterterrorism operations and training. The United States Air Force flies surveillance drones from small bases in Niger and Cameroon.
Elsewhere in Africa, the roles of special operators are varied, and their ranks are small, typically measured in the low dozens for specific missions. Between 200 and 300 Navy SEALs and other special operators work with African allies to hunt shadowy Shabab terrorists in Somalia. As many as 100 Special Forces soldiers help African troops pursue the notorious leader of the Lord’s Resistance Army, Joseph Kony. And Navy SEALs are training Nigerian commandos for action in the oil-rich delta.
The United States is building a $50 million drone base in Agadez, Niger, that is likely to open sometime next year to monitor Islamic State insurgents in a vast area on the southern flank of the Sahara that stretches from Senegal to Chad.
Mr. Trump’s tough talk on terrorism has been well received here in Chad, where American Special Operations and military instructors from several Western nations finished an annual three-week counterterrorism training exercise last week.
Many African soldiers and security forces said they would welcome an even larger United States military presence to help combat myriad extremist threats. “Of course we’d like more,” said Hassan Zakari Mahamadou, a police commissioner from Niger. “U.S. forces enhance us.”
The Pentagon has allocated about $250 million over two years to help train the armies and security forces of North, Central and West African countries.
But American aid and training alone — along with occasional secret unilateral strikes — will not be enough to defeat groups like Al Qaeda, Boko Haram and the Islamic State, officials say.
“We could knock off all the ISIL and Boko Haram this afternoon,” Gen. Thomas D. Waldhauser, the leader of the military’s Africa Command, told the Senate this month, using an acronym for the Islamic State. “But by the end week, so to speak, those ranks would be filled.”
Here on the outskirts of the Chadian capital, N’Djamena, last week, four flat-bottomed boats with mounted machine guns roared down the Chari River. The boats pulled up along the riverbank, just opposite neighboring Cameroon, and disgorged rifle-toting Chadian Special Antiterrorism Group forces and their American trainers.
In a hail of gunfire, shooting blanks, they stormed the thatched huts of a suspected Boko Haram bomb maker; seized laptops, cellphones and other material inside for clues on terrorist operations; and dashed back to the river, fending off a mock ambush on the way. Piling back into their boats under covering fire, the Chadian commandos sped off in a drill that American and Chadian officers often play out for real in the nearby Lake Chad Basin area.
“Extremism is like a cancer,” said Brig. Gen. Zakaria Ngobongue, a senior Chadian officer who has trained in France and at Hurlburt Field, Fla., and was helping oversee the exercise. “We need to continue to fight it.”