British tank hauls away a captured German artillery piece. The 15 cm schwere Feldhaubitze 13 (15 cm sFH 13), was a heavy field howitzer used by Germany in WWI. The British referred to these and their shells as "5 point 9"s or "5 9"s as the bore was 5.9 inches (150 mm). The ability of these guns to deliver mobile heavy firepower close to the frontline gave the Germans a major firepower advantage on the Western Front. About 3,500 of these guns were produced from 1913 to 1918. The Battle of Cambrai (November 20 - December 7 1917) was a British campaign of WWI. Cambrai 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. The battle was largely an artillery-infantry engagement that achieved surprise and technical superiority against strong fortifications but weak German infantry and artillery defenses, which were quickly reinforced. The British attack demonstrated that the Hindenburg Line could be penetrated.
