How the Second World War Was Fought

The war opened with a new way of fighting. Blitzkrieg, meaning lightning war, concentrated tanks into a narrow spearhead that punched through weak points in enemy lines rather than attacking along a broad front. Aircraft flew ahead and overhead, widening that breach, bombing roads, rail lines and command posts so defenders could not regroup or resupply. Infantry and support units followed behind to hold the ground the tanks had already broken open. Poland fell in weeks in 1939, and France fell in six weeks in 1940, because no army had yet learned to counter this speed.

Germany invaded the Soviet Union in June 1941 under the codename Barbarossa, expecting another fast collapse. Instead the front stretched for four years, from the outskirts of Moscow and the siege of Stalingrad in 1942 and 1943, through the Soviet counteroffensives that pushed west through Ukraine and Poland, to the fall of Berlin in May 1945. That long grind exposed the limit of blitzkrieg: it won battles but could not win a war against an enemy with enough space, population and factories to absorb the first blow and rebuild. By 1943 the United States and the Soviet Union together were out-producing Germany and Japan in tanks, aircraft and ships by enormous margins, and that gap mattered as much as any single battle.

In the Pacific, the United States practiced island hopping: capturing a chain of strategically placed islands with air bases while deliberately bypassing heavily fortified ones that could be cut off and starved of supply instead. This saved time and lives while still closing the distance toward Japan. Both fronts show the same shift the unit traces throughout: modern war was decided as much in shipyards and factories as on any battlefield.