Designed in the early 1930s, the Dornier Do.17 was one of the most important German bombers during the first years of the war. The Do.17 Z was its most advanced version, with a new cockpit design, extended to insert a rear firing gunner, new more powerful engines, and more effective defensive armament. First adopted in 1939, the Z-version was also used for reconnaissance missions and as a night fighter. The Z-wversion was extremely resistant to enemy weapons and able to execute disengagement dives at high speed.