And today, gunmen reportedly yelling "Allahu Akbar" stormed the Radisson Blu hotel in Mali's capital and seized several dozen hostages. U.S. special operations forces are "currently assisting hostage recovery efforts," a Pentagon spokesperson said, and U.S. personnel have "helped move civilians to secured locations, as Malian forces clear the hotel of hostile gunmen."

In Mali, groups like Ansar Dine and the Movement for Unity and Jihad in West Africa have long posed a threat. Major terrorist groups in Africa include al Shabaab, Boko Haram and al Qaeda in the Islamic Magreb (AQIM). In the wake of the Paris attacks by ISIS, attention has been drawn to ISIS affiliates in Egypt and Libya, too. But what are the dozens of other groups in Africa that the Pentagon is fighting with more special operations forces, more outposts, and more missions than ever?

For the most part, the Pentagon won't say.