The U.S. military secretly deployed a small number of trainers and advisers to Somalia in October, the first time regular troops have been stationed in the war-ravaged country since 1993, when two helicopters were shot down and 18 Americans killed in the “Black Hawk Down” disaster.

A cell of U.S. military personnel has been in the Somali capital of Mogadishu to advise and coordinate operations with African troops fighting to wrest control of the country from the al-Shabab militia, an Islamist group whose leaders have professed loyalty to al-Qaeda, according to three U.S. military officials.

The previously undisclosed deployment — of fewer than two dozen troops — reverses two decades of U.S. policy that effectively prohibited military “boots on the ground” in Somalia. Even as Somali pirates and terrorists emerged as the top security threat in the region, successive presidential administrations and the Pentagon shied away from sending troops there for fear of a repeat of the Black Hawk Down debacle.