The Kayaba autogyro was one of the first armed rotarywing aircraft to be used operationally in WW2. While not a helicopter, this unique aircraft was able to fly with very short takeoffs and landings. Its impact on WW2 was negligible, but it had unique capabilities that proved useful for spotting and reconnaissance.

If you re interested in learning more:
https://ja.wikipedia.org/wiki/%E3%82%...

A surviving example of the Kellett KD1 exists at the Yanks Air museum in California, USA.
https://yanksair.org/