WASHINGTON — Amid a surge of Islamic militancy in North Africa, a team of fewer than 50 U.S. special operations troops with a single helicopter arrived at a remote base in western Tunisia last month.
Their mission: train Tunisian troops in counter-terrorism tactics.
The operation was one of dozens of U.S. military deployments in Africa over the last year, often to tiny and temporary outposts. The goal is to leverage American military expertise against an arc of growing instability in North Africa and many sub-Saharan countries, from Mali in the west to Somalia in the east.
The small-scale operations by the Pentagon's six-year-old Africa Command reflect an effort to avoid provoking anti-U.S. militants in the region — and wariness of getting drawn into new conflicts after 13 years of war in Iraq and Afghanistan. U.S. commanders for Africa face tight limits on the forces and equipment they can put on the ground or in the air, despite responsibility for a vast geographic area.
Classified guidance approved by the White House last fall called for the Pentagon to "deter" terrorist attacks from Africa on U.S. territory, facilities or allies without creating a large military footprint, according to officials who spoke on condition of anonymity to discuss classified material.
Based in Stuttgart, Germany, Africa Command has only about 2,000 military and civilian personnel assigned to coordinate U.S. defense programs in about 38 African countries, although 5,000 or more U.S. troops are frequently on the continent for operations and training missions.
It's still a tiny fraction of the combined forces under Central Command, which oversees the war in Afghanistan and bases in the Middle East, or under Pacific Command, which has become a Pentagon priority since the White House announced a strategic "rebalancing" of forces to Asia in 2012.
U.S. military commanders working in Africa thus rely on small teams of special operations troops, U.S.-trained forces from friendly African countries, and European allies, especially France, that have stepped up their own military presence and operations.
In Niger, for example, U.S. and French air forces based at an airport in Niamey, the capital, are flying unarmed Reaper drones to gather intelligence. They conduct aerial surveillance across several Saharan countries where some members of the Tuareg minority group have joined Islamist warlords and farther south in Nigeria, U.S. military officers say.
Three violent extremist organizations are the chief U.S. concern. Al Qaeda in the Islamic Maghreb is active in northern and western Africa, especially Mali, and is considered the greatest threat to Americans.
But U.S. troops also are advising the Nigerian army as it establishes a special operations command to combat Boko Haram — which has launched hundreds of violent attacks across Muslim-dominated northern Nigeria — and supporting African Union troops against extremist Shabab militants in Somalia.
The U.S. command acknowledged in January that it had sent a small team of advisors to Somalia in December, the first time American troops have been stationed there since militia fighters in Mogadishu, the capital, shot down two helicopters and killed 18 U.S. servicemen in the 1993 "Black Hawk Down" incident.
"Most of the countries we're dealing with don't want a large U.S. presence," said Army Lt. Col. Robert E. Lee Magee, the commander of a 130-soldier "crisis response" unit stationed in Djibouti, a tiny former French colony in the Horn of Africa, where the U.S. maintains its only major military base on the continent. National Security Advisor Susan Rice is scheduled to visit the base this weekend.
Known as the East Africa Response Force, Magee's unit was formed after the September 2012 attacks on a U.S. diplomatic compound and nearby CIA base in Benghazi, Libya. Africa Command was unable to send troops in time to help CIA and State Department security personnel fend off militants who stormed the compounds and left four Americans dead, including Ambassador J. Christopher Stevens.
If a U.S. diplomatic post in East Africa comes under attack or U.S. citizens need to be quickly evacuated, Magee said, his unit can deploy within 18 hours and up to 1,500 miles from Djibouti.
Another new quick reaction force of 550 Marines, stationed at an air base in Moron, Spain, is charged with responding to crises in North and West Africa, officials say. The force has six V-22 Ospreys, tilt-rotor aircraft that take off and land like helicopters, as well as two refueling tankers. They give the Marines the capability to fly thousands of miles to remote locations in Africa, said Col. Scott Benedict, the commander.
The Pentagon said Friday that the Spanish government had approved an expansion of the force to 850 Marines in April, with the number of aircraft increasing to 16.
Both units were sent to South Sudan in December to help evacuate Americans and guard the U.S. Embassy after fierce fighting broke out between rival armed factions.
But the operation also highlighted the risks the Pentagon faces when it seeks to intervene with light forces in remote places. Three Ospreys were hit by gunfire and had to abort their mission.
The operation in Tunisia highlights another challenge.
Government security forces have been battling militants from the banned Islamist movement Ansar al Sharia, one of the radical groups to emerge since the 2011 "Arab Spring" uprising that ousted President Zine el Abidine ben Ali. Tunisia has seen a sharp increase in suicide attacks and assassinations in the last two years.
But because of Tunisian government concern that the presence of U.S. soldiers could provoke public opposition, the Americans operate far from the deserts of southern Tunisia, Algeria and Libya, where attacks by rebel groups, tribal gangs and Islamist militants, some with ties to Al Qaeda, have been increasing, the officials say.
"They're not able to do a whole lot, and they are in a place where there isn't a lot of activity," said a senior military officer who requested anonymity in discussing sensitive details of the U.S. force in Tunisia.
Anne Wolf, a Tunis-based analyst who has written for the U.S. Military Academy's Combating Terrorism Center, said even a small number of U.S. troops could inflame Tunisia's tense security situation.
"Any involvement of foreign troops would risk provoking further responses from violent Salafists," she said, referring to Tunisia's Sunni Muslim extremists. "It would confirm their allegations that the government is controlled by foreign powers who are meddling into Tunisian affairs."
Except for major exercises, Africa Command officials normally don't announce deployments for reasons of operational security. They confirmed the current mission in western Tunisia, but the statement had few details, including how long the troops would remain.
"At the request of the government of Tunisia," U.S. troops are conducting "an episodic training event … after months of planning" that "improves the capabilities of Tunisian forces to protect civilians from current and emerging threats," the statement reads.