Phoney War (September 3, 1939–April 9, 1940)
Known to the French as the “drôle de guerre” and to Germans as the Sitzkrieg, this period of military inactivity along the Western Front followed expiration of British and French ultimata to Berlin on September 3, 1939, issued over the German invasion of Poland. The usual image of the period in Britain is that the Royal Navy began the hard fight at sea while the bulk of the French Army sat in deep bunkers and fortifications along the Maginot Line, a picture of magnificent ineffectiveness in sky-blue tunics. It is true that such inactivity frittered away morale and cost parts of the French Army their fighting edge. It is additionally true that the dour mood infected the British Expeditionary Force, which was keeping powerful French mobile forces company on the northern flank, as the Allies awaited a Belgian invitation to move to the Dyle Line. It is also correct that Western air forces were under orders not to bomb, but instead dropped propaganda leaflets over the Ruhr in a nonbelligerent activity that did not prevent Germans shooting down Allied planes and killing crews. Still, to focus on inaction on the Western Front obscures what was really underway as the Wehrmacht finished its brutal occupation, pacification, and partition of Poland in partnership with the Red Army, then transferred its Panzer divisions to the west in readiness for FALL GELB, the campaign to conquer France and the Low Countries.
Allied planners wrongly believed that they were behind Germany in armaments production and readiness. Their strategy was to hold the Wehrmacht in place by assuming a defensive posture while France completed full mobilization and acquired modern aircraft from the United States, and Britain rapidly built up the BEF. Meanwhile, Allied navies were ordered to attrit German shipping and impose a total blockade that would crack the German economy, which was—also falsely—believed to be already straining under full war production. It is critical to understand that where Adolf Hitler and OKW still thought in terms of a speedy Vernichtungskrieg (“war of annihilation”), the Western Allies from the start thought in terms of another Materialschlacht like the one of 1914–1918. Their estimate of the length of the new war was a minimum of five years. It was also believed that nothing could be done to stop Poland being overrun, it appears that aggressive action was not even considered. Like Serbia in 1914, another small nation for whose right to national existence the Western Allies went to war, Poland surely would be overrun by its more powerful neighbor. It could be restored, it was thought in Western capitals, only upon the defeat of Germany. Belgium played a critical role during this period, refusing entry prior to a German attack and thus confirming the French High Command view that no such attack in the west should be attempted alone or before the BEF was in Flanders in real force. That would take a year or more. If the Germans chose to waste their armies attacking France's powerful defenses during that time, as they had done in five 1918 offensives that finally broke the back and spirit of the Reichswehr, that was the very purpose for which the border forts of the Maginot Line were built. The end of phony war began with Wehrmacht invasions of Denmark and Norway on April 9, 1940. All hell then broke lose on May 10, with all-out Blitzkrieg that announced FALL GELB had begun.