May 10th, 1940: Germany unleashes its Blitzkrieg upon the western Allies. Six weeks later, the war ends in a smashing German victory. Four Allied national armies have vanished. The tiny Dutch and Belgian armies, pulverized in battle, have surrendered. Great Britain rescues most of the soldiers in the BEF, but their heavy weapons and vehicles remain on the beaches of Dunkirk. The island nation begins to re-arm, but for now is out of the fight. The proud French Army, with many regiments tracing an unbroken lineage back to the 1600s, suffers the most catastrophic defeat of modern times before France surrenders.

How did this happen? The Germans, realizing they could not win a repeat of World War One, set about reinventing the offense. Their formula included massed tank formations, an air force dedicated to close tactical support, and most importantly, a command and control system based on the use of radios. Allied tanks and soldiers were often equal or superior to their German counterparts – when given the opportunity to properly deploy and prepare. Unfortunately, such opportunities were few and far between. The Germans had securely positioned themselves inside an Allied decision making process that often took days to execute, rapidly concentrating, overwhelming defenders and then exploiting success. Certainly there were answers to every German innovation, but in six short weeks the Allies did not have the time to find them. Case Yellow is a simple, but accurate, simulation recreating this monumental campaign.