 Although the AATTV was mostly involved in training the South Vietnamese forces, a few had been attached to the Combined Studies Division, run by the CIA as a counter-insurgency organisation.Serong later became a counter-insurgency advisor to General Paul Harkins, Commander US MACV, but this relationship ended under Pollard's successor, Lieutenant General John Wilton, who reduced Serong's autonomy while continuing to grant him considerable latitude.In May 1963 Serong accepted an invitation to visit the US Special Warfare School in North Carolina, informing the Military Board only after doing so, and he later visited West Germany to become familiar with intelligence activities there, again without informing Wilton, who reacted angrily after finding out about it from a newspaper report.