The German invasion of Poland on 1 September 1939 sparked the start of World War II in Europe. Days later, France and the United Kingdom declared war on Germany. Despite the Allied declaration of war, little was done to counter the German invasion of Poland. The resulting inaction led to what became known as the Phoney War. The Phoney War lasted for eight months, and no significant operations were launched (the French had launched a ground offensive into the Saarland following the German invasion of Poland, but were forced to withdraw after nine days of fighting). This changed following the German invasion of Denmark and Norway. Allied troops designated for operations in Finland, were diverted to support Norway in expelling the Nazis. On 10 May 1940, Germany launched its offensive into France and the Low Countries. Within 45 days of fighting, France would fall, leaving the United Kingdom the last free Allied power in Western Europe.
With France occupied, the United Kingdom was the next target for German aggression. Hitler planned to take out Britain with an amphibious assault on the island. Dubbed Operation Sealion, the Germans planned to use nearly 30 divisions to attack the United Kingdom. Because of British air and naval power, Hitler ordered an intensive air campaign to precede Operation Sealion, and on 10 July 1940 the Battle of Britain began. For three months, British and Allied aircraft defended the skies over the island, preventing Germany from gaining air superiority. The German failure in the Battle of Britain prevented Operation Sealion (it was eventually cancelled) and the troops designated to assault the island were sent to other theaters.
While the Germans lost the Battle of Britain and called off Operation Sealion, this did not ease the burden on the United Kingdom. German U-boats hunted and sunk thousands of merchant ships bringing vital supplies to the island. Dubbed the Battle of the Atlantic, this naval campaign has been called the longest, largest, and most complex naval battle in history. For five years, Axis and Allied naval forces clashed in the Atlantic. By the end of the war, the Allies had lost 175 warships, 3,500 merchant ships, and 741 aircraft. The Axis naval forces lost over 780 warships (largely submarines) and over 30,000 sailors in the battle.
On 6 June 1944, the Allies launched Operation Overlord (the Allied assault on northwestern Europe). Millions of Allied troops flooded into northern France from 6 June until the end of August 1944. With the western front open, and the Germans suffering catastrophic losses in the east against the Soviet Union, the war would be over in 11 months.
Look for more information regarding the British stand against the Axis in World at War issue #47 with the article “Hitler’s Greatest Mistake: The Survival of Great Britain” and join the conversation on Facebook!