World War II in Europe

France fell in six weeks in 1940 because Allied planners expected a repeat of the First World War: a slow push through Belgium, met by fixed defenses. Instead German armored divisions drove through the Ardennes forest, a hilly, wooded area judged too rough for tanks and left thinly guarded. Panzers raced to the English Channel, slicing the Allied line in two and trapping British and French forces in Belgium while the rest of the French army scrambled uselessly farther south. This was blitzkrieg: tanks punched holes, aircraft struck supply lines and spread panic ahead of the advance, and radios let commanders on the ground react instantly, exploiting a breakthrough before the enemy could regroup. Trenches had frozen the Western Front in 1914-1918 because communication was slow and firepower favored defense. Radio broke that stalemate by letting fast-moving units act on real-time information instead of waiting days for orders.

The same speed that conquered France failed in the Soviet Union. Operation Barbarossa in June 1941 pushed deep into Soviet territory, but vast distances, harsh winters, and Hitler's divided objectives slowed the advance. At Stalingrad in 1942-1943, Soviet forces encircled and destroyed the German Sixth Army, a defeat Germany never reversed. From there Soviet forces fought steadily westward, reaching Berlin by 1945.

Production decided the outcome as much as tactics. The United States and Soviet Union eventually out-built Germany in tanks and aircraft by enormous margins, flooding fronts with material Germany could not match. The Normandy landings in June 1944 opened a second major front in the west, and Allied armies broke out across France that summer, squeezing Germany between two advancing fronts until its collapse in 1945.