The Siegfried Line was a mammoth wall of German defences that stretched from the Swiss border in the south to Aachen in the north, approximately 300 miles long and, in places, up to 20 miles deep. Built by Nazi Germany between 1936 and 1938, over 500,000 workers were involved in its construction. This book provides a detailed historical background to the Siegfried Line, and a guide to what is left to see of it today. The line was not designed to thwart a full-scale offensive, but rather to delay any attack sufficiently to allow the German reserves to mobilize. In the "phoney war" (1939-40) it was effective enough to prevent the French from launching a pre-emptive strike when German forces were heavily engaged in Poland. Certain sections of the defences saw some fo the fiercest fighting of World War II. Many of the defences have since been dismantled, but some still remain today.