In March and April we wrote about the efficacy of mercenary forces in certain conflict situations. The Council on Foreign Relations' Africa in Transition blog has an article describing how a merc outfit from South Africa has provided backbone for the Nigerian Army in its fight against Boko Haram rebels.
This is a very old story in Africa, one repeated many times. Even some of the same personalities are back for another round of derring-do. No Mad Mike Hoare this time, just Eeben Barlow of Executive Outcomes fame.
For a tongue-in-cheek discussion of mercenaries, see How to Take Over a Small Country in 10 Easy Steps at the War on the Rocks website. The scenario spun there could actually work, given a bit of luck.