History research taken from The Story of the 27th Division by John F. O'Ryan.

The 102nd Field Signal Battalion was first mustered into Federal Service in spring of 1916 during the Mexican Punitive Expedition, when it was designated the 1st Battalion Signal Corps. While stationed in Texas, the battalion established radio communications in Fort Sam Houston in San Antonio, allowing command to communicate without building telegraph lines.

The battalion was again mustered into Federal service following the entry of the United States into World War I in July of 1917. Men of the 102nd Signal Battalion trained at Camp Wadsworth and maintained communications between units throughout the area, particularly between Camp Wadsworth in South Carolina and the infantry and artillery ranges at Glassy Rock. They also constructed a twelve-mile telephone line connecting the two ranges. Members of the battalion entered Liaison School, studying how to maintain communications between units and how to use technical equipment such as “the buzzer, the telephone, pigeons, flares, rockets, panels, radio, runners, message bombs, wigwag, semaphore and balloon observation.” (133)

O’Ryan notes that thanks to its experiences in Texas in 1916 and its thorough training at Camp Wadsworth, the 102nd Field Signal Battalion was extremely well prepared for the war in Europe, but was handicapped by equipment shortages.

On May 17, 1918, the 102nd Field Signal Battalion departed from Newport News, Virginia, for Europe aboard the USS Pocahontas. They arrived in France on June 3, and boarded trains for Noyelles. The entire division had assembled in the Rue area of the Somme by June 10. At the Somme, the men of the 102nd Field Signal Battalion were exposed to frequent German shelling and could predict the caliber of a shell and where it would land based on its sound.

During the 27th Division’s participation in attacks along the Hindenburg Line, beginning on September 24, the 102nd Field Signal Battalion maintained the infrastructure of army communications by repairing damaged wires. Following a brief rest after the capture of the outer strong points of the Hindenburg line, the 102nd Field Signal Battalion joined the final thrust to its main defenses. Smoke that was deployed to defend troops from machine-gun fire obscured all visual forms of signaling, and so the 102nd Field Signal Battalion was forced to revise traditional military doctrine that emphasized flags, heliographs, and lamps. O’Ryan writes of the 27th Division’s reliance on runners during the offensive: “It all means that in a great modern battle the army, in the transmission of messages and orders in the forward areas, had to revert in the main to the methods employed by Hannibal and Caesar, to go no further back in history.” (331)

The 102nd Field Signal Battalion was again invaluable during the Allied pursuit of the Germans across the Le Selle river on October 17 when they were challenged by the rapid advance of the front line beyond communications infrastructure. Under heavy fire, troops from the 102nd laid wire for telephones up to the front line at Arbre Guernon. For his service, the British Government awarded Colonel Hallahan the Distinguished Service Order.