A snapshot of Cambodia's fall, from an American diplomat evacuated from the besieged capital of Phnom Penh in 1975.

NAME: Timothy M. Carney

HOMETOWN: Washington, D.C.

CAMBODIA EXPERIENCE: Political officer at the U.S. Embassy, key in organizing the helicopter evacuation of nearly 300 people. He tried to persuade Cambodian government leaders to flee but nearly all of them stayed behind, only to be executed by the Khmer Rouge shortly after the Americans pulled out.

LIFE AFTER CAMBODIA'S FALL: Went on to ambassadorships in Sudan and Haiti, among other postings. He oversaw reconstruction efforts in Iraq after the 2003 war, assisted in elections in Afghanistan and aided Haiti after the 2010 earthquake. His career in the Foreign Service and on international affairs spanned 46 years. Carney was often critical of Washington's policy toward the countries in which he served.

REFLECTIONS: "I didn't analyze it then. I was just focusing on what I had to do to get people out of there," he says of the evacuation. Today, he views U.S. failures in Cambodia as "a consequence of bad policy and worse implementation." He says the lessons of those mistakes were forgotten by the architects of U.S. intervention in other countries, including Iraq and Afghanistan. "The United States does not have the talent and knowledge to implement the kinds of overarching policies that our political leaders pronounce. We just don't have that ability," he says.