The UN’s first peacekeeping mission, which started in 1948, was to keep a truce after the creation of Israel. Seven decades later, that mission continues, and the total number of peacekeeping operations worldwide has grown to 16, deploying more than 100,000 military personnel. Most are in Africa; the largest, in the Democratic Republic of Congo, involves 18,900 blue helmets.

Contributions to the cost of peacekeeping are worked out using a complicated formula that includes economic heft; America pays more than a quarter of the total, and the top ten countries account for four-fifths between them. But when it comes to personnel, the pattern is very different. Since some of its men were killed when a helicopter was shot down in Somalia in 1993, America has almost stopped sending troops; it now has only 74 military personnel involved in peacekeeping, only half of them soldiers.

Altogether, the top ten budget contributors supply only 6% of personnel; African and Asian countries provide the lion’s share. Tiny Rwanda contributes 6,140 military personnel but almost no money. The UN pays countries $1,330 a month per soldier, meaning that peacekeeping is lucrative for poor nations.