World War I was the Golden Age of the railway gun. More railway artillery pieces were used during this war than in any other conflict, even though at the start of the war none of the armies had railway guns and the very idea of railway artillery was comparatively new. The impetus to build and field railway-mounted guns came from the stalemate of trench warfare. The first railway guns--fielded by the French army in early 1915--were simple, improvised designs made by mounting surplus coastal defense, fortress, and naval guns onto existing commercial railway carriages. These first guns were...