September 1939: Phony War

After the German invasion of Poland, on 1 September 1939, the Allies did nothing. Britain and France both declared war on Germany on 3 September, but did not conduct any offensive operations on the Western Front. British and French forces, including aircraft, remained on their side of the frontier and did not meaningfully engage Germany until the German invasion of France and the Low Countries in May 1940.

Poland had made two assumptions going into the Second World War: that Poland could beat Germany and that France and Britain would invade Germany to capture the Rhineland, thus ending the war. Both of these assumptions proved incorrect. As Polish forces were outmaneuvered by German tanks and under fire from German airplanes, it was clear that defeat could only be avoided by British and French intervention. At this point, the Siegfried Line was still weak and Hitler’s invasion plans left it stripped of defenders, so any Allied offensive would have succeeded.

Neither Britain, France, nor Germany actually wanted to fight the war as it existed. Britain and France had both sought to avoid war with Germany and Chamberlain had believed his threats regarding Poland would be enough to deter war. But now Britain and France were committed to war. For his part, Hitler didn’t want to be at war with Britain and avoided attacks on Britain in hopes that they would end hostilities, allowing him to fight a war against France alone. Additionally, with the ongoing war in Poland, Germany was not in a position to attack Britain or France.

The British and French response was conditioned by their overestimation of German military strength. Britain and France believed that any war with Germany was likely to be on a scale of the First World War. This had a profound impact on their strategic thinking, as both Britain and France expected a prolonged war, lasting years, in which Poland was not a significant player. Britain and France thus based their strategy on the experience of the First World War. Believing that Germany had a massive military, they believed that any Allied offense would be doomed. Accordingly, the correct response was defensive. British and French troops should hold defensive positions and resist German attack while Britain and France completed their own rearmament programs, gathered additional allies, imposed a blockade on Germany, and raised massive armies from their colonies. Only once they were rearmed, had more allies, and had raised a huge army would the Allies attack Germany.

Fear of the German air force was particularly strong and had the most basis in fact since, although still weaker than the combined French and British air fleets in 1939, the Luftwaffe was the most advanced, experienced, and relatively largest branch of the German military. Britain and France believed that Germany had a capability to destroy their cities and industrial bases through air bombing. They did not bomb Germany factories or towns out of a fear that this would trigger retaliation that the Allies would be unable to defend against and that would cripple their war efforts.

As a result of their inaction, Poland was defeated by Germany. If the Allies had attacked during the war with Poland, they almost certainly would have destroyed German defenses along the Rhine and ended the war. Instead, when Britain and France did fight Germany in May 1940, they fought an army that had undivided focus and had finished looting Polish armories. The German army in 1940 was significantly stronger than it had been in 1939, having an additional 9 months of rearmament and the equipment stores of the largest army in eastern Europe.