'Mission impossible': UN in Cambodia shows early limit of nation building

Just over 30 years ago, a crackling radio in a refugee camp on the Thai border brought Sam Sophal word that the United Nations was coming to his war-ravaged homeland of Cambodia.

For Sam Sophal, who survived the Khmer Rouge genocide only because his mother bribed Khmer Rouge executioners with her silver watch, the promise of peace was irresistible.

The UN Transitional Authority in Cambodia (UNTAC) arrived on March 15, 1992, with great expectations, the first UN nation-building operation after the collapse of the Soviet Union sparked hope that democracy would flourish around the world.

But long before...