Meanwhile our left or northern wing on this vast battle-front
had begun its final advance on the Hindenburg or Wotan line east of Arras. It may be as well to explain that the Hindenburg line was constructed during the battle of the Somme when it became evident that the old line of 1914 could not be held for long. The new line, from the Vimy ridge north of Arras, ran southward across the Scarpe and Sensee, then eastward to Mceuvres, and then south- eastward in front of Cambrai to St. Quentin and La Fare, whence it was connected by the St. Gobain hills and the Chemin des Dames to the Champagne front. But the Higher Command feared that the northern part of the line would not resist a British attack. An inner line was therefore constructed, running from behind Lens through Drocourt to Queant, a mile or two east of Bullecourt on the main Hindenburg line. This "switch " line was unfinished when, at the Battle of Arras in April, 1917, our troops broke through the outer defences, as the Germans had foreseen. However, by a great effort, the enemy resisted our advance until the " switch " was complete. The main line at Bullecourt gave us infinite trouble, and we did not approach the " switch " itself last year.
