Even as Obama administration officials vowed to hunt down the hostage-takers in Algeria, they faced the added challenge of a dauntingly complex jihadist landscape across North Africa that belies the easy label of “Al Qaeda,” with multiple factions operating among overlapping ethnic groups, clans and criminal networks.

Efforts to identify and punish those responsible for the attack in Benghazi, Libya, where Ambassador J. Christopher Stevens was killed in September, have bogged down amid similar confusion. The independent review panel investigating the Benghazi attack faulted American spy agencies as failing to understand the region’s “many militias, which are constantly dissolving, splitting apart and reforming.”

Although there have been hints of cross-border alliances among the militants, such links appear to be fleeting. And their targets are often those of opportunity, as they appear to have been in Benghazi and at the gas facility in Algeria.

In the longer term, the Obama administration and many analysts are divided about what kind of threat the explosion of Islamist militancy across North Africa poses to the United States. Some have called for a more active American role, noting that the hostage-taking in Algeria demonstrates how hard it can be to avoid entanglement.