This week marks the 50th anniversary of the beginning of a mass slaughter in Indonesia. With American support, more than 500,000 people were murdered by the Indonesian Army and its civilian death squads. At least 750,000 more were tortured and sent to concentration camps, many for decades.

The victims were accused of being “communists,” an umbrella that included not only members of the legally registered Communist Party, but all likely opponents of Suharto’s new military regime — from union members and women’s rights activists to teachers and the ethnic Chinese. Unlike in Germany, Rwanda or Cambodia, there have been no trials, no truth-and-reconciliation commissions, no memorials to the victims. Instead, many perpetrators still hold power throughout the country.

Indonesia is the world’s fourth most populous nation, and if it is to become the democracy it claims to be, this impunity must end. The anniversary is a moment for the United States to support Indonesia’s democratic transition by acknowledging the 1965 genocide, and encouraging a process of truth, reconciliation and justice.

On Oct. 1, 1965, six army generals in Jakarta were killed by a group of disaffected junior officers. Maj. Gen. Suharto assumed command of the armed forces, blamed the killings on the leftists, and set in motion a killing machine. Millions of people associated with left-leaning organizations were targeted, and the nation dissolved into terror — people even stopped eating fish for fear that fish were eating corpses. Suharto usurped President Sukarno’s authority and established himself as de facto president by March 1966. From the very beginning, he enjoyed the full support of the United States.