With the unrelenting violence in places such as South Sudan and Somalia, the world seems to have overlooked the people of Sudan's Nuba Mountains, where for several years President Omar al-Bashir waged war against his own people. A few years ago on a near-daily basis, Russian-made Antonov planes bombed unarmed civilians, injuring and killing them, as well as burning small, thatched-roof houses and crops that would have fed the Nuba people in this remote region. Most of the medical staff of international aid agencies left the mountain region, but one doctor stayed. Dr. Tom Catena, who came from...