The Maginot Line
Nearly two million French troops manned the Maginot Line in May 1940 supported by a quarter of a million British. The fortified line, named posthumously after the 1922 French Minster of War, combined man made defences with natural terrain and stretched from the Swiss to the Belgian frontiers. It was meant to prevent a repeat of the First World War by stopping a German invasion on its borders. France had suffered more than most in the Great War as its very land had been reduced to a battlefield between warring European powers.
But Hitler flanked the line by invading Holland and Belgium on 10 May. German blitzkrieg tactics leave allied forces in the North scrabbling to evacuate a crumbling France. The troops stationed along the Maginot Line, intended to heroically defend their stations until French reserves could be mobilised, are largely reduced to stranded onlookers.
On 25 June, all hostilities cease and France surrenders. It had taken under two months to defeat the French nation. Their impenetrable Maginot Line had simply been avoided, surrounded and neutralised.