The Focke-Wulf Triebflügel, or Triebflügeljäger, literally meaning "thrust-wing hunter", was a German concept for an aircraft designed in 1944, during the final phase of World War II, as a defence against the ever-increasing Allied bombing raids on central Germany.
It was a vertical take-off and landing tailsitter interceptor design for local defense of important factories or areas which had small or no airfields.
Focke-Wulf Triebflügel
A tail-sitter, or tailsitter, is a type of VTOL aircraft that takes off and lands on its tail, then tilts horizontally for forward flight.
The Convair Pogo was one tailsitter design.