The U.S. military was closely tracking a one-eyed bandit across the Sahara in 2003 when it confronted a hard choice that is still reverberating a decade later. Should it try to kill or capture the target, an Algerian jihadist named Moktar Belmoktar, or let him go?

Belmoktar had trained at camps in Afghanistan, returned home to join a bloody revolt and was about to be blacklisted by the United Nations for supporting the Taliban and al-Qaida. But he had not yet, at the time, attacked Americans, and did not appear to pose a threat outside his nomadic range in the badlands of northern Mali and southern Algeria.

Military commanders planned to launch airstrikes against Belmoktar and a band of Arabs they had been watching in the Malian desert, according to three current and former U.S. officials familiar with the episode. But the ambassador to Mali at the time said she vetoed the plan, arguing that a strike was too risky and could stir a backlash against Americans.