Ultimately though, I think part of the reason for the Fall of France and its Defeat was that it contributed so many resources to the Magniot Line that would otherwise have been able to be used to fight Germany on its own terms. The French were caught off-guard when the Germans swung through Poland, Belgium and the Lower Countries as they were expecting Germany to invade on the German/French border. Thus it was this crucial lack that the French seemed to be preparing for WW1 and the wrong sort of adversary. If it had been Stalin and the Russians, the Magniot Line may have been effective and caused ultra-heavy casualities, but as it is the German Commanders looked at their map and saw a way to avoid that massive defensive line. I think the British may have played a big part in creating the situation of the Phoney War where Germany and Hitler were still deciding what they wanted to do and how to accomplish it. It could be that the British presence played a part in delaying the total collapse of France quicker, also there was the fact that Vichy France signed a treaty with Germany very quickly. I think there was already some negotiation going on behind the scenes already and it was only a matter of time before something became of it. One of the biggest things that changed after the Fall of France and Dunkirk, in the Eastern Desert was the issue of Mobility. There we start to see the taking of the fight to the enemy through the LRDG or Long Range Desert Group which acted as a form of hit and run sabotuers of the Allies, striking at key targets and pinning down some German forces and providing information on others. I think the Fall of France proved to the British High Command why the old tactics would not work. Also the Commandos in Europe and the American versions were a reaction to this new type of warfare as I see it. I also thought that the Fall of France demonstrated once and for all to the British High Command that they must support their infantry, tanks and trucks from the air, or see them knocked out. At the very least in the Desert we at least see the beginnings of Close Air Support for tanks and troops. Therefore Dunkirk was the medicine that the Allied planners needed to take to see that the old WW1 style of battle would not work. The Soviets though were using adapted WW1 style battle tactics by throwing masses of infantry and tanks against the Germans in a fairly unequal fight and winning, but for the Allies I think this plan would have led to a situation where Germany would win the whole of Europe and be able to keep it as a WW1 Commander would have flung his troops against the Atlantic Wall. Therefore, Dunkirk it was also necessary for the British to salvage what they could so they could use that to regenerate what was left of their shattered army.