PHNOM PENH, Cambodia, Aug. 1 — More than 27 years after the mass killings and after nearly a decade of wrangling between Cambodia and the United Nations, formal proceedings have begun against surviving leaders of the brutal Khmer Rouge regime. On July 10, a special prosecutor’s office opened its investigation into one of the last century’s most sustained atrocities, in which 1.7 million people died from 1975 to 1979 through torture, systematic killings, overwork, starvation and disease. A first shipment of 383,149 pages of evidence, contained on 524 reels of microfilm, was delivered to the prosecutors on July 17. snip......