Dunkirk is located in the north of France. With a seaside location near the borders of three European powers, making it a site of centuries of commerce travels as well as battles.
Nazi Germany invaded the Netherlands, Luxemburg, and Belgium in a "Blitzkrieg" ("lightning war") and the war ended on May 10th, 1940. The German air power and ground forces supported by Panzer tanks occupied Luxembourg on May 10, Netherlands by May 14 and Belgium at the end of the month.
Soon after, the Allies expected Germany to attempt on invading France through the Maginot Line, but in fact, the German troops went through the Ardennes Forest along the Somme Valley towards the English Channel, considering the Strait of Dover, having a distance of 21 miles between England and France across the English Chanean located to the southwest.
Eventually, German forces cut off communication and transport between the northern and southern branches of Allies forces, leading to the Allied troops getting pushed into a small sliver of the French coast. By May 19, the tension led to the commander of the British Expeditionary Force (BEF), General John Gort considering evacuating all forces by the sea in order to ensure unexpected attacks from the Nazi troops.
In the meantime, the British Prime Minister Neville Chamberlain resigned due to pressure on May 12, which led to Winston Churchill making way for new strategies. Thus Churchill at first opposed the idea of evacuating together with French forces until BEF and its allies backed out on the French port of Dunkirk 10 km from the Belgian border leading to Churchill evacuating as well.
On May 24, Adolf Hitler made the decision to halt German panzers from further advancing down Dunkirk due to the german generals worry over possible Allied counterattack such as the one on May 21 south of Arras as well as Luftwaffe commander Hermann Goering's air forces available to prevent any evacuation attempt at Dunkirk. On May 26, Hitler advances the panzers again, but by then the Allies had gotten enough time to prepare. Hitler's decision, in this case, was to the Allies' advantage.
The British used the codename "Operation Dynamo" for evacuating Dunkirk. The name comes from Vice-Admiral Bertram Ramsay leading a team working out of a room inside the Dover cliffs that had once contained a generator known as Dynamo. As promised by Luftwaffe, the harbor was bombed, which slowed the evacuation even though Ryal Air Force planes attempted to delay or stop the German planes, losing many air forces in the process.
On the first day, Operation Dynamo managed to evacuate around 7500 men from Dunkirk and around 10000 the following day. Due to Dunkirk having shallow beaches. smaller ships were used to carry troops to the larger ships further into the North Sea. About 800 t 1200 boats aided in the evacuation from Dunkirk. Churchill expected only 45000 men to be resued at most, but more than 47000 British troops were successfully rescued and more 53000 including French troops made it out by May 30.
German Federal Archives (Bundesarchiv), Bild 146-1978-062-24
By the end of the operation, 198000 British and 140000 French troops were off the Dunkirk beaches making a total of approximately 338000 men. On June 4th, German troops occupied Dunkirk as 90000 Allied forces along with the bulk of BEF's heavy guns and tanks were left behind.
The Royal Norfolk Regiment held off a German company on May 27, until their last ammunition, which led to them retreating to a farmhouse 50 miles away from Dunkirk, the village of Paradis. Forced to surrender, RNR waved a white flag tied to a bayonet as they moved out of the farmhouse but were met by German-gun fire. On their second attempt, they were ordered by an English speaking German officer to an open field where they were robbed off of their gas masks and cigarettes. Eventually, they were forced into a pit with machine guns in fixed positions. Captain Fritz Knochlein, a German officer gave the order to fire and the two surviving British soldiers were either stabbed with bayonets or shot down.
However, two Britz, Albert Pooley, and William O’Callaghan survived by laying among the dead until dark and then upon a rainstorm crawling to a farmhouse to tend their wounds. Getting fund once more by the Germans and make into POWs, Pooley was repatriated to England in April 1943 in exchange for wounded German soldiers. Pooley's story was not believed until O’Callaghan also made it home and verified the story. Thus Captain Knochlein was captured for being guilty of a war crime and hanged.
In conclusion, the German blitzkrieg was successful since France called for an armistice by mid-June 1940, the significantly large evacuation of the British troops from Dunkirk was of a big advantage for the Allies.
On June 4, 1940, Churchill gave a speech in regards to this;
“[We] shall not flag or fail. We shall go on to the end, we shall fight in France, we shall fight on the seas and oceans, we shall fight with growing confidence and growing strength in the air, we shall defend our Island, whatever the cost may be, we shall fight on the beaches, we shall fight on the landing grounds, we shall fight in the fields and in the streets, we shall fight in the hills; we shall never surrender.”
However, many French troops as well as ammunition, machine guns, tanks, jeeps, military machinery, and more were left behind at Dunkirk. Thus with Western Europe heavily disarmed, Germany advanced through France, and Paris was occupied on June 14. Within eight days, Henri Petain signed an armistice with the Nazis at Compiegne. Germany annexed half of France and left the other half to controlled French rulers.
On June 6, 1944, the liberation of Western Europe began with the successful Allied "Landing at Normandy".