From Wikipedia

 Line Of Fire - Cambrai 1917

The Battle of Cambrai (20 November - 7 December 1917) was a British campaign of the First World War. Cambrai, in the Nord département (Nord-Pas-de-Calais), was a key supply point for the German Siegfried Stellung (part of the Hindenburg Line) and the nearby Bourlon Ridge would be an excellent gain from which to threaten the rear of the German line to the north. The operation was to include an experimental artillery action. Major General Henry Hugh Tudor, commander of the 9th Infantry Division, suggested trying out new artillery-infantry techniques on his sector of the front. During preparations, J. F. C. Fuller, a staff officer with the Royal Tank Corps (RTC), was in the process of looking for a place to use tanks as raiding parties. Field Marshal Julian Byng, commander of the British Third Army, decided to incorporate them into the attack.