Tuol Sleng Security Prison 21, or S-21, was once a high school in Phnom Penh. During its “reign of terror”, the Khmer Rouge imprisoned, tortured and executed 17,000 people there. To save on the cost of bullets, they slaughtered most prisoners with pickaxes. Some were strapped to steel bedframes and electrocuted. At nearby Choeung Ek, the infamous “killing field”, they shattered babies’ skulls against trees by swinging them from their feet. Years later on a visit to Choeung Ek, I trod on bits of bone and clothing exposed in the mud by the monsoon rains. There were 196 killing fields across Cambodia.