Dozens of senior Colombian army officers implicated in the killing of 3,000 civilians falsely claimed to be rebels a decade ago have risen through the ranks and are escaping punishment for their roles in one of Latin America’s worst atrocities, Human Rights Watch said.

In a 95-page report titled “On their Watch” release on Wednesday, the rights group offers the most extensive look so far at the pattern of killings by the U.S.-backed armed forces and the legal proceedings against military personnel who tried to present civilians as guerrillas killed in combat to inflate body counts that led to promotions and bonuses.