The Siegfried Line, known in German as the Westwall (= western bulwark), was a German defensive line built during the 1930s (started 1936) opposite the French Maginot Line. It stretched more than from Kleve on the border with the Netherlands, along the western border of Nazi Germany, to the town of Weil am Rhein on the border with Switzerland. The line featured more than 18,000 bunkers, tunnels and tank traps.
From September 1944 to March 1945, the Siegfried Line was subjected to a large-scale Allied offensive.
The official name for the German defensive line construction program before and during the Second World War that collectively came to be known as the "Westwall" (and "Siegfried Line", or sometimes "West Wall", in English) changed several times during the late 1930s, reflecting areas of progress.
Border Watch programme (pioneering programme) for the most advanced positions (1938)
Limes programme (1938)
Western Air Defense Zone (1938)
Aachen–Saar programme (1939)
Geldern Emplacement between Brüggen and Kleve (1939–1940)
These programmes were all pushed forward with the highest priority, putting a heavy demand on the available resources.
The origin of the name "Westwall" is unknown, but it appeared in popular use from the middle of 1939; there is a record of Hitler sending an Order of the Day to the soldiers and the workers at the "Westwall" on 20 May 1939.
The Siegfried Line at the start of the Second World War had serious weaknesses. German General Alfred Jodl said after the war that it was "little better than a building site in 1939", and when Field Marshal Gerd von Rundstedt inspected the line, the weak construction and insufficient weapons caused him to laugh. Despite France's declaration of war on Germany at the beginning of the Second World War, there was no major combat at the Siegfried Line at the start of the campaign in the west, except for a minor offensive by the French. Instead, both sides remained stuck in the so-called Phoney War, where neither side attacked the other and both stayed in their safe positions.