Thanks to a "lurker" for the pointer to an exchange on Twitter between this lady as @texasinafrica (in a moment her bio) and others:
Laura Seay is an assistant professor of government at Colby College, where she teaches African politics. Her research focuses on advocacy groups and U.S. policy in Africa.
Just found her article in 'Slate', which is of value, especially if you look at the issues from a US political scene perspective.

She refers to:
American forces have been in Niger since 2012. Currently, there are about 800. Their primary mission is to advise and assist Niger’s armed forces in their fight against terrorist groups that attack their citizens.
So with the IISS Military Balance to hand, Niger has an army of 5,200 (with mainly French kit) and an air force with 100 (with fifteen aircraft and seven helicopters). So one US soldier for just over every six Niger soldiers. I exclude any wider, regional role and "teeth to tail" ratio.

It concludes with:
Niger is unfamiliar to most Americans, and there’s a need for a long-overdue debate about why American forces are there and in other places around the world in the borderless and seemingly endless “Global War on Terror.” Are the threats to the United States from groups like ISGS really significant enough to spend billions of dollars deploying troops to fight them? Should lives be risked and lost in service of murky goals that often seem tangential to U.S. interests? These are questions worth asking.