In 1917 following declaration of war against Germany, the United States began building its one million-man military force through a wide-spread draft and all eligible U.S. citizens and resident foreign nationals were swept into the U.S. Army.Particularly paranoid of America's "melting pot," the Allies warned the American Expeditionary Forces (AEF) G-2, Maj. Dennis Nolan, that U.S. forces needed to be safeguarded from internal and external threats of enemy espionage, sabotage and subversion.On July 11, 1917, Nolan wrote to the Chief of Staff of the Army requesting "that fifty secret service men, who have had training in police work [and] who speak French fluently, be enlisted as sergeants of infantry in service in intelligence work and sent to France at an early date."Nolan also requested 50 company-grade officers to assist British and French counter-espionage efforts at French ports and on the front lines. Both requests were approved the following month and the Corps of Intelligence Police (CIP) became the first official recognition of the counterintelligence discipline in the U.S. Army.The first 50 CIP agents arrived in France in November 1917. Two months later, the AEF received authorization to recruit another 700 agents from units already overseas. By the armistice in November 1918, however, the CIP had only reached a strength of 418 agents.One third of CIP agents served in the Front Zone, where the U.S. Army had responsibility for 123 miles of territory adjacent to the fighting. They established mobile checkpoints to prevent entry of non-combatants into the combat zone and secured France's border with neutral and Allied countries.Other agents served directly with advancing troops of the First and Second Armies where their chief mission was to control the civil population and detect and prevent espionage. Among the first to enter recaptured towns, they immediately replaced any suspect government officials and interviewed inhabitants for enemy order of battle information.The majority of the CIP agents served with the G-2 Services of Supply (SOS) in the Rear Zone. They provided security for 14 ports in France, England and Scotland; 400 miles of frontier along the borders with Spain and Italy; 31 supply depots; and seven leave centers. They disguised themselves as laborers and interpreters to detect enemy agents circulating among U.S. troops. They also warned Soldiers about the consequences of "loose talk" and investigated suspicious behavior or cases of possible sabotage.The CIP agents in the G-2 SOS investigated 3,706 cases and neutralized 229 suspected enemy agents through conviction, internment or expulsion from the war zone.Additionally, a few CIP agents worked "Special Projects" in the Counter Espionage Section of the AEF G-2. In addition to compiling a central file of more than 160,000 names, they provided security for traveling VIPs and, at times, served as Gen. John Pershing's bodyguard.The CIP recorded a number of problems that arose during their World War I operations. Foremost, wartime haste left little time to procure suitable personnel, to adequately train agents, or to educate the rest of the U.S. Army about the need for and importance of counterintelligence. Furthermore, since CIP agents arrived in France several months after the first American combat troops, they did not have time to set up a "protective screen" to safeguard U.S. forces and support services from enemy espionage or subversion.The secret nature of much of the CIP's work meant that their successes went unrecognized, which inhibited promotions for officers and commissions for enlisted personnel and negatively impacted morale. Rank disparity often became an issue when agents interviewed senior officers or interacted with Allied counterintelligence personnel. Finally, the word "police" in the organization's title led to CIP investigations of more criminal activities than their mission required or allowed, much to the consternation of the Military Police.Despite these myriad problems, CIP agents were exceedingly proud of their service. According to their official history, "World War I experiences taught most CIP agents that it was hard, unglamorous and painstaking work that earned for the Corps of Intelligence Police a permanent and honored place in all the future wartime plans of the United States Army." This, however, did not protect CIP from post-war reductions along with the rest of the US Army.While the CIP remained a viable organization, carrying out critical counterintelligence missions in Hawaii, Panama, the Philippines and along the United States-Mexico border, the number of agents on duty from 1920 to 1940 ranged from just 18 to 40. Unfortunately, the same wartime haste that plagued effective operations in World War I would cause similar problems in World War II.