In 1983, a college history teacher told me that in his view, the next major conflagration would happen in South Africa, where the black majority was agitating to throw off the oppressive rule of the white South African minority.

Due to Nelson Mandela, the conflagration never happened. 

"Blessed are the peacemakers." Mandela was a peacemaker. He presided over the transition in power in South Africa without exacting revenge for the horrific offenses of apartheid. It is one of the great achievements in statecraft of the last 100 years. 

Wars which don't happen don't get the headlines of those which do. 

But avoiding war is a supreme achievement, always to be honored. 

Neville Chamberlain's "peace in our time" was a phony achievement. Mandela's avoidance of war in South Africa was real, and lasting.

(Avoiding war with Iran is also a great achievement, by the way.)

The rush to war is an evil thing. Mandela knew it. He knew the radical forgiveness needed to avoid such a war, and he exercised it. Only one who suffered as he had possessed the moral authority to convince others to forgive as well.