It was a direct order from the Führer. On the 24th of May, the Allied forces were in critical condition. 9 British and 10 French divisions were completely surrounded, Belgium was on the brink of defeat. It seemed that everything was in the Germans' hands, and, suddenly, an order came right from the Führer. Halt.
The idea to stop all ground attacks originally came from Rundstedt. Most generals were extremely disappointed even then, but the final say was Adolf's, and he agreed with Rundstedt, that it would not be smart to send the Panzer divisions through the swamps of Flandria. He was paranoid. Scared by the incredible speed of the Blitzkrieg, he was obsessed by the idea that his Panzers would be surrounded. Seeing this panic as an opportunity, Göring chimed in, promising that his Luftwaffe would take care of Dunkirk, and pressing the Führer even further to let the Panzer divisions rest and prepare for the 'second round'. It was all just greed for glory. The amazing Blitzkrieg was made possible with help from the Luftwaffe, sure, but all the glory still went mostly to the Panzer divisions. Göring wanted a piece of that glory, of that recognition, so he tried to steal at least Dunkirk. He reassured the Führer that his Luftwaffe had it all under control, and that the land forces really were not needed for Dunkirk. So Göring and Rundstedt basically made this decision alone, and Adolf just went with it.
Even though it seems like absolute foolishness now, back then, Rundstedt actually had acceptable reasons to halt the attack. Firstly, the Nazis didn't actually know just how many soldiers there were in Dunkirk. They expected around 100k, at most. Rundstedt had no idea what an opportunity it was, he didn't think he had anything to lose, and the Panzers really did need a break. So, Dunkirk seemed insignificant. Everyone believed that the Brits would not come back to fight, anyways. And, lastly, they had faith in the Luftwaffe, who really didn't do Göring's promises any good, because the RAF was an equal match for them, so, in the end, with the ground forces halted, and the battles in the air being a stalemate, most Allied soldiers were evacuated from Dunkirk.
Hey there,
Just to let you know, your question is fine, and we're letting it stand. However, you should be aware that questions framed as 'Why didn't X do Y' relatively often don't get an answer that meets our standards (in our experience as moderators). There are a few reasons for this. Firstly, it often can be difficult to prove the counterfactual: historians know much more about what happened than what might have happened. Secondly, 'why didn't X do Y' questions are sometimes phrased in an ahistorical way. It's worth remembering that people in the past couldn't see into the future, and they generally didn't have all the information we now have about their situations; things that look obvious now didn't necessarily look that way at the time.
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