From Jeffrey Gettleman in The Times:
The United Nations, which has 3,000 combat-ready peacekeepers in South Sudan, tracked the advancing fighters from helicopters for days before the massacre and rushed in about 400 hundred soldiers. But the peacekeepers did not fire a single shot, saying they were vastly outnumbered and could have easily been wiped out.
It had been my understanding that United Nations peacekeeping soldiers were supposed to risk their lives in order to save the lives of innocent people. Not so, apparently.