Here is another perspective on the role of the telephone and the observation officer. It comes from Arthur Empey’s “Tommy’s Dictionary of the Trenches.”
“Telephone. A little instrument with a wire attached to it. An artillery observer whispers something into this instrument and immediately one of your batteries behind the line opens up and drops a few shells into your front trench. This keeps up until the observer whispers, ‘Your range is too short.’ Then the shells drop nearer the German lines.” (1)
Friendly fire — being shelled by your own side — was a reality. Tim Cook describes the Canadian fighting in June 1916:
“[They] had to deal with the terrifying experience of friendly fire. While the gunners tried to support the attack, they had little idea as to where the Canadian or German lines were after the lines had shifted. Shells were therefore continually falling short onto Canadian troops. This added to the men’s confusion and terror, especially since veterans could easily pick out the sound of the Canadian shells that were supposed to be hurtling towards the enemy, and instead were crashing among them. Attempts to call off these short barrages usually failed, as runners ‘sent with messages seldom ever lived to deliver them.'” (2)
(1) Empey, Arthur Guy. Over the Top by an American Soldier Who Went. 1918.310
(2) Cook, Tim. At the Sharp End. Canadians Fighting the Great War Vol. 1 1914-1916. 2007.360.
The painting “Observation of Fire” is by Colin Gill, who described it as showing “Gunner officers correcting their battery fire by field telephone from a disused trench in No Man’s Land.” Gill was originally in the Royal Garrison Artillery but was invalided out. The painting is from the Imperial War Museum.