PHNOM PENH, Cambodia (AP) — Cambodians were bluntly reminded of their tragic history Monday as the trial began of three top Khmer Rouge leaders accused of orchestrating Cambodia’s “killing fields” in the late 1970s.

After Judge Nil Nonn declared the trial open, the prosecution started its case at the U.N.-backed tribunal — more than three decades after the Southeast Asian country witnessed some of the 20th century’s worst atrocities.

An estimated 1.7 million people died of execution, starvation, exhaustion or lack of medical care as a result of the Khmer Rouge’s radical policies, which essentially turned all of Cambodia into a forced labour camp as the movement attempted to create a pure agrarian socialist society.

The defendants are old and infirm, and there are fears they won’t live long enough for justice to be done.

On Monday, they sat side by side with their lawyers in the courtroom especially built for the tribunal, as the prosecutors read opening statements describing the scope of their alleged crimes.

Present were 85-year-old Nuon Chea, the Khmer Rouge’s chief ideologist and No. 2 leader; 80-year-old Khieu Samphan, an ex-head of state; and 86-year-old Ieng Sary, the former foreign minister. They showed little reaction as a litany of charges was read out against them.