In 1980 I visited the dilapidated provincial capital of Takeo, near Phnom Penh. My mission was to learn about Ta Mok, also known as the Butcher, whose name struck terror into the people of the region. I walked across a narrow bridge towards the middle of a small lake, where a three-storey brick building had served as his headquarters during the Pol Pot years. I found a middle-aged man squatting under a coconut tree. I asked him if he had ever seen Ta Mok. “You mean A Mok?” he retorted — the despicable Mok, not grandpa Mok. “He was a monster. He killed people like ants.” He rubbed his calloused foot in the dirt to make the point.

Ta Mok, commander of the South-West Zone, appears only a few times in Heng Samrin’s autobiography, but the Butcher who emerged as Pol Pot’s main executioner had an early brush with Samrin. In his autobiography, the first of a major figure in modern Cambodia, Samrin reveals that trouble with Mok went back a long way; there was always suspicion about Vietnam or anybody associated with it. Perhaps that suspicion about Eastern Zone cadres who came in touch with the Vietnamese explains why two groups of men from Samrin’s unit sent to collect herbal medicine from the hills controlled by Mok disappeared in 1973 — long before the conflict between the Vietnamese and the Khmer returnees from Vietnam burst into the open. Talking with the historian Ben Kiernan in 1991, Samrin was more emphatic. “From 1974 we resisted Pol Pot on the question of Vietnam,” he said.

Samrin inquired about the missing men and Mok said he knew nothing, but enigmatically added that he arrested only enemies. “We never saw our soldiers again,” Samrin notes in his typical laconic style. Shortly thereafter, the Khmer Rouge infantry of the two zones fought pitched battles with mortars, which signalled for the first time the bloody struggle that would tear the country asunder. Samrin’s autobiography offers many such nuggets, but its brevity and narrow focus will disappoint experts looking to piece together the country’s tormented history.

• Tags: Cambodia, Heng Samrin, Issue 15, Nayan Chanda