In January 1967, Peng was taken to his first "struggle session" in which he was paraded in chains before several thousand jeering Red Guards, wearing a large paper dunce cap and with a wooden board hung from his neck on which his "crimes" were written. In the fall, Peng was held at a PLA military prison outside Beijing and was allowed to receive extra clothing. In July, Mao and Lin Biao, co-operating with Jiang Qing's faction, ordered the PLA to form an "investigation group" to determine Peng's "crimes" so that Peng could be more thoroughly humiliated in future struggle sessions. Peng's jailers attempted to force Peng to confess that he was a "great warlord," a "great ambitionist," and a "great conspirator" who had "crept into the Party and the Army." Peng refused to confess to those accusations or to "surrender to the masses" and so his jailers strapped Peng to the floor of an unlit cell and did not allow him to stand or sit up, drink water, rise to go to the toilet, or move in his sleep for several days. After Peng still refused to "confess," his jailers began routinely beating him and broke several ribs, injured his back, and damaged his internal organs, especially his lungs. Peng's violent "interrogations" lasted over ten hours a day, but his interrogators were replaced every two hours to keep them from developing any sympathy for Peng, a practice pioneered by the Stalinist secret police in the 1930s. Peng was "interrogated" that way over 130 times. During interrogations he shouted denials to the Red Guards who beat him, and it is reputed that he pounded the table so hard that the cell walls shook.