In the beginning of 30s it was appeared in the world an idea of high-speed bomber that could outstrip contemporary fighters. One of the objectifications of this conception became the twin-engine bomber Do 17 designed by a German Dornier Flugzeugwerke company.
Since the beginning of 1939 it were produced Do 17Z planes with new “Waffenkopf” type nose part and air-cooled Bramo 323 Fafnir engines.
In 1940 it were produced some Do 17Z-7 Kauz I night fighters. These planes had powerful nose-fired armament. They served in the night fighter unit I/NJG 2 up to the beginning of 1941.