In September 1976, Keo Meas, who had been tasked with writing a history of the party, was arrested as a result of disputes over the foundation date of the party and its reliance on Vietnamese support. Under torture at Tuol Sleng he confessed that the date chosen was part of a plot to undermine the party's legitimacy and was then executed. In late 1976, with the Kampuchean economy underperforming, Pol Pot ordered a purge of the ministry of commerce, and Khoy Thoun and his subordinates who he had brought from the northern zone were arrested, tortured, and at Tuol Sleng before being executed. Khoy Thoun confessed to having been recruited by the CIA in 1958. The center also ordered troops from the eastern and central zones to purge the northern zone killing or arresting numerous cadres.