BEIJING — On a spring evening in 1989, with the student occupation of Tiananmen Square entering its second month and the Chinese leadership unnerved and divided, top army commanders were summoned to headquarters to pledge their support for the use of military force to quash the protests.

One refused.

In a stunning rebuke to his superiors, Maj. Gen. Xu Qinxian, leader of the mighty 38th Group Army, said the protests were a political problem, and should be settled through negotiations, not force, according to new accounts of his actions from researchers who interviewed him.

“I’d rather be beheaded than be a criminal in the eyes of history,” he told Yang Jisheng, a historian.

Although General Xu was soon arrested, his defiance sent shudders through the party establishment, fueling speculation of a military revolt and heightening the leadership’s belief that the student-led protests were nothing less than an existential threat to the Communist Party.