Islamist terrorist groups have found a new home and it's not in the Middle East -- it's in Africa. Specifically, the Sahel, a band of territory in West Africa between the Sahara desert and the savannah. Since the early 2000s, Islamist extremist groups have increasingly strengthened their base here -- training fighters, raising money, and launching a massive number of attacks. Some are linked to al-Qaeda and other Islamic State. This is throwing these already weak countries into crises and making the region one of the most dangerous in the world.