Why Didn’t the Allies Attack Germany in 1939? Unpacking the Phoney War

The declaration of war on Germany by Britain and France in September 1939 should have signaled an immediate, all-out conflict. Yet, for months, an eerie calm settled over the Western Front, leading to a perplexing question that has puzzled historians and enthusiasts alike: why didn’t the Allies attack Germany in 1939?

This period, famously dubbed the “Phoney War” or “Sitzkrieg,” was far from an actual truce. Instead, it was a complex mix of strategic considerations, deeply rooted military unpreparedness, profound political caution, and a fundamental misunderstanding of Hitler’s true intentions. To truly grasp why the Allies didn’t launch a significant offensive, we must delve into the multifaceted reasons behind this agonizing delay.

The Immediate Aftermath of War Declaration

The catalyst for war was unequivocal: Germany’s invasion of Poland on September 1, 1939. This brazen act triggered declarations of war from Britain and France just two days later. The world held its breath, anticipating a swift Allied response.

However, the German Blitzkrieg in Poland was shockingly swift and brutally efficient. Within weeks, Poland fell, leaving little time for a concerted Allied response in the East. This rapid collapse profoundly impacted the strategic calculus on the Western Front, ultimately contributing to why the Allies didn’t attack Germany in 1939 directly from the West.

Key Reasons for Allied Inaction

The lack of an immediate, forceful Allied offensive – the crucial question of why didn’t the Allies attack Germany in 1939 – was not due to a lack of will, but rather a confluence of deeply ingrained beliefs and practical limitations.

1. The “Phoney War” (Sitzkrieg) Mentality

The term “Phoney War,” or “Sitzkrieg” (sitting war), aptly describes the eight-month period of military inaction from September 1939 to May 1940. During this time, there were no major land operations on the Western Front, despite both sides technically being at war[1].

Allied strategists, still heavily influenced by the First World War, believed a long war of economic attrition and naval blockade would eventually force Germany to surrender. They envisioned a “waiting game” where Germany would be worn down without the Allies committing to costly, bloody frontal assaults reminiscent of the Somme or Verdun. This strategy further cemented the decision for why the Allies didn’t attack Germany in 1939, opting for a prolonged economic squeeze rather than direct confrontation[2].

2. Defensive Military Doctrine and Strategy

France, in particular, had invested heavily in the Maginot Line, an elaborate system of fortifications along its border with Germany. This defensive masterpiece was designed to deter invasion and funnel any German attack through Belgium, allowing France time to mobilize and Britain to deploy its expeditionary force. The Maginot Line fostered a deeply defensive mindset, discouraging offensive operations directly against Germany’s industrial heartland.

The collective memory of WWI’s devastating trench warfare and massive casualties still loomed large over both British and French military and political leaders. This profound fear of heavy losses made any offensive operation highly unappealing. Allied doctrine, therefore, favored a defensive posture, allowing them to build up forces and resources, rather than launching a premature and potentially disastrous offensive against an already mobilized Wehrmacht.

3. Allied Military Unpreparedness

Despite the looming threat, neither Britain nor France were fully prepared for a large-scale offensive in 1939. Britain, in particular, was still in the early stages of rearmament. Its army, the British Expeditionary Force (BEF), was relatively small and not fully equipped for an immediate, major offensive operation on the continent. The focus had been more on naval power and the Royal Air Force.

The French Army, while larger, was perceived as slow, poorly mechanized, and still reliant on World War I tactics. It was simply not suited for a rapid, mobile offensive against Germany’s modern, mechanized forces. Mobilizing and supplying an offensive force capable of breaching German defenses, an essential step if the Allies were to attack Germany in 1939, would have been a monumental and time-consuming task in late 1939.

4. Economic Warfare and Naval Blockade

Both Britain and France placed significant faith in the long-term strategy of economic warfare. They believed that a naval blockade, cutting off Germany’s access to vital resources and raw materials, would cripple its economy and eventually force them to negotiate or collapse, much as it had contributed to Germany’s defeat in WWI. This strategy diverted immediate military resources and attention away from a direct land offensive, as the Allies expected the blockade to be a decisive factor in the war’s outcome[3].

5. Political Caution and Hopes for Negotiation

The shadow of the appeasement era still loomed large over Allied political leaders. Figures like British Prime Minister Neville Chamberlain, who had sought to avoid war at all costs, still harbored hopes for a negotiated peace, even after the invasion of Poland. There was a strong desire to avoid a total, devastating war if at all possible.

Public opinion in both Britain and France also played a role. There was limited appetite for another devastating land war, especially after the perceived failures of intervention in Czechoslovakia and the rapid fall of Poland. The political will for a full-scale offensive was not robust, particularly given the enormous perceived risks and potential human cost.

6. Rapid Collapse of Poland

The speed of Poland’s defeat was a critical factor. Poland fell too quickly for the Allies to launch any meaningful diversionary attack from the West that might have relieved pressure on the Poles. By the time any substantial offensive could have been contemplated, Poland was already overwhelmed and largely under German control. Direct military aid to Poland was logistically impossible, making a Western Front offensive the only theoretical option, which then faced all the aforementioned hurdles[4].

The Consequences of Inaction

The period of Allied inaction had profound and largely negative consequences. Germany was allowed to consolidate its gains in Poland, secure its eastern flank, and freely transfer forces to the Western Front without facing a concerted counter-attack. This crucial respite allowed Hitler to prepare meticulously for his future offensives, first against Scandinavia and then, decisively, against France and the Low Countries.

By not attacking, the Allies ceded the strategic initiative to Germany, allowing Hitler to dictate the timing, location, and nature of the next phase of the war. This loss of initiative, combined with the psychological impact of the “Phoney War” on troop and public morale, set the stage for the devastating events of 1940, where the true cost of their initial hesitation became brutally clear.

The question of why the Allies didn’t attack Germany in 1939 is complex, revealing a mix of rational strategic calculations, grave misjudgments, and the enduring trauma of past conflicts. It highlights how nations, even when declared at war, can find themselves in a limbo of inaction with far-reaching consequences.