Niger, like much of West Africa's Sahel region, is struggling with a deepening security crisis as groups with links to al Qaeda and Islamic State carry out attacks on the army and civilians.
The US has long had a military role in Africa, but much of it was in the shadows.
Four Americans were killed on a mission in northern Niger when their convoy was ambushed returning from Tongo Tongo.
US soldiers fight alongside French forces and locals in Niger.