The desert sands of Mali and Algeria provide an unlikely arena for an existential challenge to the global alliance system the United States has managed since World War II. But the hesitant and timid U.S. and European Union responses to the crisis in northwestern Africa drip like acid on the rock of alliance cohesion.

The Obama administration's self-described preference to lead from behind in messy conflicts in the Islamic world has much value for war-weary, financially strapped Americans. But great care must be taken with that approach to avoid driving U.S. leadership into a strategic dead end.

After days of very public hesitations by Washington and Brussels to provide even nonlethal help — such as in-air refueling — to France's reluctant intervention in Mali, the U.S. and the 27-nation European Union committed just four transport aircraft to the effort. That will intensify doubts abroad about the administration's intentions and effectiveness in getting others to step forward again.