BEIJING — For three decades, Jiang Lin kept quiet about the carnage she had seen on the night when the Chinese Army rolled through Beijing to crush student protests in Tiananmen Square. But the memories tormented her — of soldiers firing into crowds in the dark, bodies slumped in pools of blood and the thud of clubs when troops bludgeoned her to the ground near the square.

Ms. Jiang was a lieutenant in the People’s Liberation Army back then, with a firsthand view of both the massacre and a failed attempt by senior commanders to dissuade China’s leaders from using military force to crush the pro-democracy protests. Afterward, as the authorities sent protesters to prison and wiped out memories of the killing, she said nothing, but her conscience ate at her.

Now, in the run-up to the 30th anniversary of the June 4, 1989, crackdown, Ms. Jiang, 66, has decided for the first time to tell her story. She said she felt compelled to call for a public reckoning because generations of Chinese Communist Party leaders, including President Xi Jinping, have expressed no remorse for the violence. Ms. Jiang left China this week.

[New documents show power games behind Tiananmen crackdown.]

“The pain has eaten at me for 30 years,” she said in an interview in Beijing. “Everyone who took part must speak up about what they know happened. That’s our duty to the dead, the survivors and the children of the future.”