The Dornier Do 335A did not meet all the Luftwaffe requirements. First, the cockpit armor was too weak, which excluded the machine from the role of a fighter intercepting heavily defended Allied bombers. Therefore, in the summer of 1944, a modified version of the Do 335 - marked with the letter B- was developed. The main difference was to be an armored pilot's cockpit with a new, easier to manufacture windscreen. The front wheel had larger tire. To be able to retract it without any changes in the landing gear bay construction, it was rotated around the leg axis by 45 Degrees during the retraction. The rest of the equipment and weapons were to be the same as in the case of the Do 335A-1. The developed version was designated Do 335B-1, but it was quickly abandoned in favor of heavily armed versions B-2 and B-3, known as Zerstoerer. The prototypes of the version B-2 were Do 335M-13 and M-14 powered, like the A-1, by the DB 603E (front) and DB-603QE (rear) engines, but with significantly reinforced armament. The 15 mm MG 151/15 cannons above the engine were replaced with a 20 mm MG 151/20, and the wings were fitted with two 30 mm MK 103 cannons with 70 rounds per barrel. The same cannon fired through the propeller axis.