Over the past several years, French troops have battled Al Qaeda’s North Africa affiliate and other Islamist extremists in Mali, and have helped African troops thwart Boko Haram, a violent militancy that has spilled from Nigeria to attack Chad, Niger, and Cameroon. The Islamic State is also a looming threat. In the latest sign of an emerging regional collaboration, five countries within the Sahel — Mauritania, Mali, Burkina Faso, Niger, and Chad — announced recently that they would create three border areas for military patrols and operations. French troops are advising and assisting these units. The Trump administration, which is already fighting the Islamic State in both Iraq and Syria and weighing whether to send several thousand more American troops to Afghanistan to fight the Taliban, has been only too eager to continue Obama-era policies of providing financial, logistical and intelligence support to France in this region. By doing so, it hopes to avoid having to put American combat forces on the ground in yet another global hot spot. American and French officials say their close military and counterterrorism partnership will continue unchanged after the election last week of Emmanuel Macron as France’s next president.