World War I: Overseas
In France, the American Expeditionary Forces developed its own intelligence organization. General John J. Pershing selected COL Dennis E. Nolan as head of the intelligence section of the AEF General Staff, thereby making Nolan, in effect, the Army’s first G2. The widespread use of radios for the first time significantly improved military communications. It also allowed the opportunity to obtain intelligence through interception of messages—for both sides. Communications security (COMSEC) was an obvious necessity, but the Army entered World War I with little experience in this area and inadequate means of encoding message traffic. The Army’s Signal Corps cipher disk, which was equivalent to the Confederate cipher disk of 50 years before, furnished little security. To meet its COMSEC needs, the AEF established the Code Compilation Section. By the time the AEF entered battle, it had been provided with the River and Lake Codes. Codebooks were distributed down to regimental level, and codes were changed every 2 weeks to prevent compromise. However, it was not enough to issue codes–it was also essential to ensure they were being used. For the first time in its history, the Army issued security guidelines and monitored telephone lines and radio circuits to detect any lapses in transmission security.