As an example of the growing cooperation between the Pentagon and France, an American military planner will, for the first time, join the headquarters staff of the French operational command.

Having France, with its deep cultural and historical ties to the region, take the lead in counterterrorism operations here saves the United States from having to assume another major military mission. For France, the Pentagon’s aerial refueling, transportation and intelligence assistance are crucial to the operation’s success.

“Not only would that be more expensive than helping the French, but the fact of the matter is that the French are better at operating in that part of the world,” said Michael R. Shurkin, a senior political scientist at RAND and a former analyst for the Central Intelligence Agency. “As for U.S. aid to the French, the stark reality for the French is that they simply could not operate there without our help.”

But it is a risky mission for French troops and their African allies, as the departing French defense minister, Jean-Yves Le Drian, said while visiting troops in Mali, Niger and Chad in February. Mr. Le Drian cited the expanding support and partnerships with regional forces and noted the terrorist threats that plague these desperately poor countries, which have difficulty enforcing their loosely guarded borders against extremists.

“Unfortunately, our fight against jihadist groups is not a fight against a regular army,” Mr. Le Drian said in Niamey, Niger’s capital. “Whatever your success on the ground, it does not protect us from an attack.”

Mali is perhaps the most striking illustration of that chaos. In 2012, Mali’s north fell under the control of Qaeda-linked jihadist groups that hijacked an ethnic Tuareg-led rebel uprising, though the Islamists were largely ousted by a French-led military operation in January 2013.