A century of Army cryptology and signals intelligence

  • Published
  • By Lt. Col. Yukio A. Kuniyuki III
  • 344th Military Intelligence Battalion

The years 2017 and 2018 mark the centennial for U. S. Army involvement in World War I.  They also commemorate 100 years of ground-based signals intelligence collection and the use of cryptology to support major combat operations.


“This source of information, practically unthought-of before the war, has been developed to such an extent that, at the close of hostilities, it constituted one of the main branches of intelligence,” said Capt. Charles H. Matz, Radio Intelligence Officer, First Army, American Expeditionary Forces, November 1918.


When the United States entered WWI, radio intelligence was a nascent capability first deployed during Gen. John J. Pershing’s Mexican Punitive Expedition from 1916-17.  During the Mexican campaign, Gen. Pershing’s forces used ‘radio tractors,’ purchased by the Signal Corps in 1914, to intercept and monitor transmissions by the Carrancista forces.


A year later in France, the American Expeditionary Force, also led by Gen. Pershing, developed a viable radio intelligence capability to support the St. Mihiel and Meuse-Argonne offensives.  By the Armistice in 1918, with the help of British and French experts, the AEF had approximately 500 soldiers who could effectively collect, decrypt, analyze and report on enemy radio transmissions.


During the war, there were two types of radio intercept stations: one focused on ground communications networks, and one focused on aerial communications.  These earliest intercept stations located within a kilometer of the front were primarily manned by Signal Corps soldiers and were often nothing more than a wooden shack or a wheeled-jalopy with an antenna and a radio.


These static and mobile intercept stations provided goniometric radio direction finding, decryption, and traffic analysis to identify order of battle, disposition, or troop movements.  Similarly, the aerial communication intercepts informed Allied air pursuit squadrons on enemy artillery positions.  The stations performed an additional function of monitoring friendly networks to identify breaches in information security.


More notably, radio intelligence would not have been successful without support from the burgeoning field of cryptology spearheaded by Col. Ralph Van Deman during his effort to re-establish the Military Intelligence Division. 


Recognizing a desperate need for cryptologists, Van Deman recruited Herbert O. Yardley, a former State Department code clerk, to lead his Code and Cipher Bureau modeled after the British Army Intelligence structure and designated MI-8.  To build capacity within MI-8, Yardley and Van Deman solicited the assistance from George Fabyan and his Riverside Laboratories located in Geneva, Illinois.  Riverside specialized in cryptology and graduated three classes by Spring of 1918.


By the end of the war, the MID had grown from two officers and two clerks to a total strength of 282 officers, 250 enlisted personnel, and 1,157 civilians.


100 years later, the efforts of Van Deman, Yardley and the pioneers of SIGINT live on.  The SIGINT professionals today continue to find, know, and never lose the enemy in an increasingly complex world defined by technology, information, and cryptology.  The young men and women today continue to be the point of the spear, the key to victory, and Soldiers of the new millennium.


For more information on the history of the U. S. Army Military Intelligence Corps or Signals Intelligence, check out the following website at the National Museum of the United States Army.