Throughout the first eight months of World War II, there was just one short military ground action on the Western Front, when French troops invaded Germany's Saar territory. Then, on 1 September 1939, Nazi Germany invaded Poland; the Phoney Period began with the United Kingdom and France declaring war on Nazi Germany on 3 September 1939, with little real conflict following, and concluded with the German invasion of France and the Low Countries on 10 May 1940. Even though Britain and France did not engage in large-scale military action, they did launch economic warfare, particularly with the naval blockade, and shut down German surface raiders. In addition, they devised intricate plans for a slew of large-scale operations aimed at crippling Germany's war effort. These included establishing an Anglo-French front in the Balkans, invading Norway to control Germany's key iron ore source, and launching an oil strike against the Soviet Union. Unfortunately, only the Norway plan came to fruition, and it was too little, too late by April 1940.
A few Allied actions broke the silence of the Phoney War. First, the French launched the Saar Offensive in September to aid Poland, but it burned out after a few days and retreated. Next, the Soviets attacked Finland in the Winter War in November, prompting great debate in France and Britain about launching an operation to assist Finland. The forces finally prepared for this war were postponed until March. Finally, the German invasion of Denmark and Norway in April came from Allied negotiations regarding a Scandinavian campaign, and the Allied soldiers previously gathered for Finland were moved to Norway instead. Fighting raged there until June, when the Allies withdrew, losing Norway to Germany due to Germany's invasion of France.
The Germans began strikes at sea against British aircraft carriers and destroyers on the Axis side in the autumn and winter, sinking many, including the ship HMS Courageous, which claimed 519 lives. The Luftwaffe commenced air raids on British vessels on 16 October 1939, marking the start of aerial combat. In addition, both sides carried out some modest bombing raids and surveillance flights.
Bore War was the initial word used by British people to describe this time; eventually, both sides of the Atlantic adopted the phrase Americanism Phoney War. Even in North America, the word Phoney War is commonly spelt using the British spelling rather than the American phony. However, some American sources do not follow this pattern. The term was initially used in print in September 1939 in a US publication that used the British spelling. However, other concurrent American stories used "phony" because both spellings were in use in the US at the time. By January 1940, "phoney" had become the only proper spelling in the United Kingdom.
Winston Churchill coined the terms "Twilight War" and "Sitzkrieg" to describe the Phoney War. It's known as the drôle de Guerre in French ("funny" or "strange" war). The term "Phoney War" was most likely created by US Senator William Borah, who observed in September 1939, "There is somewhat phoney about this war," in response to inactivity on the Western Front.
Plan West, the Polish Army's overall defence strategy, projected that the Allies' offensive on the Western front would greatly relieve the Polish show on the Eastern front. Whereas most of the German Army was fighting in Poland, the Siegfried Line, a reinforced defence line along the French border, was manned by a much smaller German force. On the other side of the boundary, French and British forces faced each other along the Maginot Line, although there were only a few brief skirmishes on the ground, while fighter planes engaged in infrequent dogfights in the air. While Western Europe remained unsettling for seven months, the Royal Air Force released propaganda flyers on Germany, and the first Canadian militaries arrived in Britain.
Germany hoped to persuade Britain to agree to peace in the early months of the war. Even though London hospitals were bracing for 300,000 casualties in the first week, Germany did not target British cities by air. German pilots who struck Scottish naval bases declared they would have been court-martialed and executed if they had bombed civilians. Attacks on military targets, such as the British attack on Kiel on the second night of the war, resulted in severe aircraft losses for both sides. They also feared reprisal for the civilians they bombed. Germany used 90% of its frontline planes during the Polish invasion, which Britain and France were unaware of. Civilian attitudes toward Germany in Britain were still not as hostile as they would become after the Blitz. A German Heinkel 111 aircraft crashed near Clacton-on-Sea, Essex, on 30 April 1940, killing the crew and injuring 160 civilians on the ground. With the support of the Royal Air Force, the staff was laid to rest in the local cemetery. Wreaths with condolence inscriptions were placed on the coffins. While German troops waved at them, British airmen mapped the Siegfried Line.
While Leopold Amery recommended that the Black Forest be decided to bomb with torches to burn its ammunition dumps, Kingsley Wood, the Secretary of State for Air, stunned the member of parliament by stating that the forest was "private property" and could not be bombed, nor could weapons factories, because the Germans might do the same. In 1939, several British commanders stationed in France brought packs of foxhounds and beagles, but the French government prevented their attempts to introduce live foxes. Britain and France purchased massive weapons from American manufacturers at the onset of hostilities, boosting their output. Discounted sales from the non-belligerent US helped the Western Allies.
Despite its relative tranquillity on land, the conflict was genuine on the high seas. The British liner SS Athenia was destroyed off the Hebrides just hours after the declaration of war, killing 112 people at the beginning of the long-running Battle of the Atlantic. The Allies established a blockade of Germany on 4 September to prevent her from importing food and raw materials to continue her war effort; the Germans responded with a counter-blockade, while the Soviet Union assisted Germany with supplies bypassing the blockade. The RAF Bomber Command, Britain's main offensive force, was also extensively involved. Still, daytime bombing inflicted minor damage and resulted in unsustainable casualties, such as when 12 out of 22 Wellington bombers were shot down over the Wilhelmshaven naval station on 18 December 1939.
At the Nuremberg tribunal, German military leader Alfred Jodl stated that Germany did not collapse in 1939. The West's approximately 110 French and British divisions were held dormant against the 23 German divisions throughout the Polish campaign. According to General Siegfried Westphal, the German Army could only have held out for one or two weeks if the French had struck in force in September 1939.
The Saar Offensive was a French operation against the German 1st Army in the Saarland. Its mission was to aid Poland. After a few kilometres, the assault was called off, and the French forces withdrew. According to the Franco-Polish military pact, the French Army planned to begin preparations for a major offensive three days after mobilization began. The French soldiers were supposed to effectively control the territory between the French border and the German lines and investigate the German defences. The French Army planned to launch a full-scale assault on Germany on the 15th day of mobilization, 16 September. On 26 August, France began a preemptive rally, and on 1 September, total mobilization was declared.
On 7 September, four days afterward France declared war on Germany, the offensive in the Rhine river valley began. Since the Wehrmacht was occupied with the attack on Poland, the French forces along their border with Germany had a significant numerical advantage. Against scant German opposition, eleven French divisions advanced over a 32-kilometre line at Saarbrücken. No German forces were diverted as a result of the attack. Around 40 divisions were supposed to participate in the all-out assault, including one armoured, three mechanized, 78 artillery troops, and 40 tank battalions. The French Military had advanced to a depth of 8 kilometres and had taken roughly 20 villages that the German Army had evacuated without encountering any resistance. However, after capturing the Warndt Forest, 7.8 km2 of severely mined German territory, the half-hearted operation was called off.
The Anglo-French Supreme War Council met for the first time at Abbeville on 12 September. Because the French chose to fight a defensive war, forcing the Germans to come to them, all offensive efforts were halted immediately. Along the Siegfried Line, General Maurice Gamelin ordered French forces to stop no closer than 1 km from the German positions. This decision was not communicated to Poland. Instead, Gamelin notified Marshal Edward Rydz-Śmigły that half of his divisions had come into contact with the enemy and that the Wehrmacht had been forced to evacuate at least six divisions from Poland due to French advances. The next day, General Louis Faury, the head of the French Military Mission in Poland, advised General Wacaw Stachiewicz, the Polish Chief of Staff, that the big onslaught on the western front was scheduled for September 17–20 had to be postponed. The Phoney War began when French divisions were instructed to withdraw to their barracks along the Maginot Line.
The Winter War, which commenced on 30 November 1939, with the Soviet Union's assault on Finland, was pivotal during the Phoney War. Public opinion in France and the United Kingdom, in particular, was quick to support Finland and demand effective action from their governments in support of the brave Finns against their much larger aggressor, the Soviet Union, especially since the Finns' defence appeared to be far more successful than the Poles' during the September Campaign. The Soviet Union was ejected from the League of Nations due to its attack, and a projected Franco-British mission to northern Scandinavia was hotly disputed. The British forces assembling to send to Finland's aid were instead dispatched to Norway's aid in the Norwegian campaign before the Winter War concluded. Édouard Daladier quit as Prime Minister of France on 20 March, after the Winter War, partly due to his failure to support Finland's defence.
The Altmark Incident on 16 February concerned the Kriegsmarine and Germany by jeopardizing iron ore supplies and provided compelling grounds for Germany controlling the Norwegian coast. The German invasion of Denmark and Norway, codenamed Operation Weserübung, began on 9 April. Allied troops began landing in Norway on the 14th, but by the end of the month, the southern areas of Norway had fallen into German control. The battle in the north lasted until the Allies retreated in early June in response to the German invasion of France; Norwegian forces on the mainland laid down their arms at midnight on 9 June.
The failure of the Allied effort in Norway, which was an extension of the never-implemented intentions to help Finland, prompted a historic debate in the House of Commons, during which British Prime Minister Neville Chamberlain was constantly criticized. Chamberlain's cabinet received a formal vote of confidence of 281 to 200, but many of his followers voted against him, while others abstained. As a result, Chamberlain discovered that leading a National Government or forming a new coalition government was impossible with himself as the leader. As a result, on 10 May, Chamberlain resigned as Prime Minister but retained control of the Conservative Party. Chamberlain's replacement was Winston Churchill, who had been a vocal critic of Chamberlain's appeasement policy. Churchill formed a new coalition government, including representatives of the Conservatives, Labour, and Liberal Parties and several non-political ministers.
The majority of the main battles fought during the Phoney War took place at sea, including the Second Battle of the Atlantic, which lasted the whole war. Among the other noteworthy occurrences were:
Strategic bombardment of German industry by the RAF's large Bomber Command was envisioned as a "knockout blow" in British war plans. However, there was widespread fear of German vengeance. When President Franklin D. Roosevelt recommended a cease-fire on bombing missions that would threaten civilians, Britain and France agreed instantly, followed by Germany two weeks later. As a result, the RAF flew several combined reconnaissance and propaganda leaflet flights over Germany. In the British press, these activities were dubbed "pamphlet raids" or "Confetti War."
German forces moved into Belgium, the Netherlands, and Luxembourg on 10 May 1940, eight months after Britain and France announced war on Germany, marking the conclusion of the Phoney War and the start of the Battle of France. Italy entered the battle on 10 June 1940, aiming to acquire territory if France was beaten. Still, the thirty-two Italian divisions that crossed the French border had limited success against five defending French divisions.