The Hindenburg Line, which was developed in early 1917, was designed to have depth and flexibility. Pillboxes, bunkers and machine gun nests all played vital roles in the system, as did the counter-attacking Eingreiftruppen. Since its conception, it had been effective when used properly, but Passchendaele would be where the Siegfriedstellung would face its toughest test yet. Allied superiority in artillery and aircraft, unrelenting bad weather and exhausted soldiers all put a huge strain on the German defence system, but would they be its undoing?
