The Corps of Intelligence Police (CIP) had been in existence since 1917, and CIP agents served proudly both with the American Expeditionary Forces in Europe during World War I as well as at serving in the United States. But after that war ended, a military drawdown ensued, and the authorized number of agents dwindled dramatically. When Congress passed the Selective Service Act on 16 September 1940, authorizing an increase in Army strength to 1,640,000 men in less than a year, the CIP had only 42 trained investigators with a mission of providing internal security for a force of millions.

Two problems faced the Corps: finding qualified personnel and training them. The Secretary of War issued an order to open a CIP Investigators Training School in Washington DC. Located in a single room at the Army War College at Fort McNair, the school accepted its first students on 24 February.

Soldiers were recruited who were between 22 and 33 years of age, had at least a high school diploma (college education preferable, with training in law or accounting), had completed basic military training, and it was hoped that potential agents would already have previous experience as an investigator in some governmental or law enforcement agency. The authorization jumped from 42 to 188, Major Garland Williams reported for duty as the Commandant of the School and CIP Chief, and the school opened its doors.

Students were taught principles of observation and description, espionage and counterespionage, bombs and "infernal machines," undercover work, and other investigative topics. A total of 61 separate courses and practical problems were listed in the course of study prepared for the first class. Thirty-nine men successfully completed the first course; nine failed.

On 7 October 1941, the school moved to Chicago and its name was changed to CIC Investigators Training School after the CIP became the Counter Intelligence Corps in January 1942.