You’ve heard of Darfur, and you know about the slaughter underway in Syria. But the worst ethnic cleansing you’ve never heard of is unfolding in the Nuba Mountains of Sudan, where the government is bombing villages, schools and hospitals and trying to keep out food and medicine.

It doesn’t get much coverage, partly because it’s difficult to get access to. But when you’ve seen these atrocities, they haunt you. So we slipped into the Nuba Mountains through rebel lines to try to document the killings. This video is the result.

President Obama will visit Africa this month, and we’re hoping that he’ll raise this issue with regional leaders and make a big push for humanitarian access — especially to get vaccines and medicines in. So watch the video, read the columns and help spread the word about what’s going on.