In October 1941, several unsuccessful raids carried out by the Soviet Air Force against the Romanian oilfields convinced Hitler to conquer the Crimean Peninsula. The first difficulty lay in the Russian position on the Perekop Isthmus. Obviously, the 51st Army had fortified this natural 5 mile wide route to the south of the peninsula. Impossible to bypass the obstacle, it had to be taken by with a frontal assault. At 5:00 AM on 5 October, German artillery unleashed a rolling thunder barrage over enemy lines.