Why did the Germans allow the defeated British forces to escape from Dunkirk in the Battle of France?

Before answering this question, one must look first at why Germany and England were at war at the time. After the end of WW1, both Germany and Prussia (a close German ally with German speaking people) lost large amounts of resource rich territory to other countries, including Poland, France, Denmark, Belgium and Czechoslovakia. After Germany rearmed and recovered somewhat from the economic woes following WW1, they began the process of regaining lost territory and uniting all German people once again into the nation of Germany. This included annexing territory that was occupied by German people, including the nation of Austria, Prussia and the territory lost after WW1 to France, Denmark, Belgium and Czechoslovakia.

Once this started taking place, England begins to deploy its British Expeditionary Force (BEF) in France to prepare for a future coordinated attack on Germany with Russia. At this point, the last portion of German land that had not been reacquired was in Poland. The land was West Prussia, Posen and Upper Silesia. The Poles refused to give the German land and population back to Germany, largely because England and France both promised Poland that they would immediately come to her defense in the event of a German attempt to retake the now Polish controlled territory. Germany declares war, and retakes its lost territory. Shortly after the German declaration of war, Russia attacks Poland and wipes out the remainder of the country to eliminate Poland as an obstacle for the expected future Russian attack on Germany.

England and France then declared war on Germany, as part of their promise to come to Poland's defense if it came to war over Poland's theft of German territory. This starts what is known as 'The Phony War' where war was declared, but neither side was really acting as though there was a war. Germany did not wish for war against England, France or the United States. As a result, they tried to negotiate a peace with England. The English leaders, war mongers like Churchill in particular, were not interested. Rather, they wanted to execute their planned war against Germany and their plan was right on schedule. The only thing they needed at this point was for Russia to get its forces modernized and in place.

At this phase in the conflict, England convinces Norwegian government to cut off German supplies of vital Swedish iron ore. This action resulted in a German invasion of Norway. The English and French land troops in Norway to oppose the Germans, but it is only a token defense that is unable to stop the invasion. Norway capitulated in 65 days with some of their political leaders fleeing to England in fear of retribution from the Germans for their hostile actions.

At this point, it is clear to everyone that England is preparing for an invasion of Germany. At this point the BEF had accumulated the following forces in France, and were adding more daily. 316,000 infantry, including 10 infantry divisions, three corps, the 1st Army Tank Brigade, 25,000 support vehicles, an RAF attachment of 500 combat aircraft, the 1st Light Armored Reconnaissance Brigade, the RAF Advanced Air Striking Force (AASF), and the 5th Infantry Royal Artillery division. (Clearly a large scale deployment.)

Germany cannot afford a two front war, and attacks France in an effort to eliminate the Western front before the Russians are in position to attack on the Eastern front. Germany is forced to attack France, through Belgium due to the Maginot line. The battle is over very quickly, with the French and English forces still trying to fight in a WW1 style, while Germany is using mobile warfare. The English are in full retreat to Dunkirk in order to escape.

Make no mistake, Germany could have easily crushed the remaining BEF forces. The BEF was in complete disarray with long columns of troops fleeing toward Dunkirk. The Germans had complete air superiority, and the English had no answer for the German armor and mechanized infantry tactics. While militarily it seems like a smart move for them to completely destroy the BEF, politically it would have been a disaster. (

Now, everyone knows that Germany allowed the BEF to escape and many people speculate why. The easy answer is also the most logical. Germany allowed the BEF to escape at Dunkirk intentionally. There are two possible causes for this decision, and probably both are true. One is that the Germans were indirectly given assurances by the English that they would cease the war against Germany if the remainder of the BEF was allowed to flee to England. The other is that the Germans believed that destroying the BEF completely would cause irreparable damage to relations with England and the United States. Germany realized that they likely could not win a conflict with all of the major world powers, and thus needed to establish a lasting peace if at all possible. Regardless or which, or both are true... Germany wanted peace with England, and wanted the Western war to cease. England however, clearly wanted war and knew it was only a matter of time before the Russians got involved, so maintaining a status of war was their ultimate decision ultimately resulting in WW2, Germany's defeat and the takeover of communism in most of Eastern Europe and most of Asia.