The Nazis already had a couple of massive train-mounted super cannons positioned on the French coast of the Channel, which they used to attack targets up to 29 miles away. These weapons were bad enough, but they were only part of the story. They planned and actually built superguns capable of striking at other European countries (the prototype is shown above). These superguns used the "multi-charge principle". Basically, after the projectile was fired, secondary charges of propellant also fired in quick succession to add an incredible amount of velocity to the shell. The German plan was to use 50 Vergeltungswaffe 3 superguns (called the V-3s) to bombard London from two huge underground bunkers near Mimoyecques in northern France, with the first base's full arsenal of 25 gun tubes commencing firing in October 1944. Fortunately, Allied bombing raids in July 1944 ended the construction of these superguns using deep-penetration bombs, saving London from even more pounding. But two similar guns with shorter barrels were finished and they were used to bombard Luxembourg from December 1944 to February 1945. The attacks were not particularly overwhelming: only 10 people were killed and 35 wounded. Due to the collapsing rail network, the Nazis found it hard to get ammunition to the guns and even the size of the projectiles had to be scaled back. Had the Mimoyecques guns gone into action in 1944, the Nazis would have been in a position to get more and larger ammunition to the guns. And that's a truly terrible thought to contemplate.