Over the course of its long engagement in the Democratic Republic of Congo, the United Nations has issued plenty of ultimatums. On Tuesday, it issued another one, aimed at the rebel M23 movement.

But this was different - for the first time, the threat had real teeth. Along with troops from Tanzania and Malawi, South African soldiers are on standby to go on the offensive if necessary as the most groundbreaking military development in UN history gets tested for the first time.

To understand what the United Nations is doing in the Democratic Republic of Congo, you need to go back nearly two decades, to a different country on a different continent entirely.

It is 1995, in the middle of the Bosnian war, and the United Nations peacekeeping mission, staffed by Dutch soldiers, has set up a 'safety zone' for Bosnian Muslims fleeing from Serbian forces. They needed it, and thousands of people - men, women and children - make their way into the UN camp.

But the Serb forces, led by Ratko Mladic, keep coming, and the UN peacekeepers do nothing to stop them, crippled by an institutional fear of losing their neutrality and becoming an...