Phoney War silence broke with blitzkrieg in May 1940
London and Paris entered the war against Germany on 3 September 1939 after Poland was invaded, yet months of Phoney War saw little continental fighting beyond a timid French Saar poke. In April 1940 Germany seized Denmark and Norway; in May it shattered Allied armies in France and the Low Countries.
While German strength bled into Poland, a thin force held the Siegfried Line opposite the Maginot. Britain and France scrambled to buy U.S. arms as non-belligerent factories discounted sales. Operation Weserübung beat Allied plans to Scandinavia. Then Sedan breakthroughs trapped the BEF and elite French and Belgian units; evacuation from Dunkirk through 4 June saved most British and some French troops thanks to weather, German hesitation, and a civilian flotilla crossing the Channel under fire.
Italy joined as France reeled; Philippe Pétain accepted armistice terms at Compiègne on 22 June 1940, with the ceasefire taking effect three days later. Later Western Front phases—especially 1944–45, dubbed the European Theater by Americans—would reverse the map, but the 1940 collapse defined the theatre's opening disaster from Norway to the Pyrenees in a single season.
The Western Front label covers Denmark, Norway, Benelux, Britain, France, and Germany, with Italy treated as related yet separate. Early quiet taught the wrong lesson: a declared state of war was not the same as a contested front until armour and air power made the difference in a few crushing weeks of May and June.
The arithmetic of 1940 was lopsided. In roughly six weeks the Allied armies lost over 375,000 killed or wounded and saw 1.8 million men marched into captivity, while German losses came to 43,110 dead and 111,000 wounded; Hitler had braced for a million fatalities. Paris fell on 14 June. Once the Luftwaffe failed to beat the RAF, invading Britain was shelved and work began on the Atlantic Wall along the Channel coast. The Allies probed that shore at Dieppe on 19 August 1942, a mostly Canadian raid in which nearly two-thirds of the attackers ended up killed, wounded or captured.
Source: Western Front (World War II)
