Vienna was also the center of the important resistance group around Heinrich Maier, which provided the Allies with plans for V-1, V-2 rockets, Peenemünde, Tiger tanks, Messerschmitt Bf 109, Messerschmitt Me 163 Komet and other aircraft. The information was important to Operation Crossbow and Operation Hydra, both preliminary missions for Operation Overlord. In addition, factory locations for war-essential products were communicated as targets for the Allied Air Force. The group was exposed and most of its members were executed after months of torture by the Gestapo in Vienna. The group around the later executed Karl Burian even tried to blow up the Gestapo headquarters in the Hotel Metropole.