Which concept that was similar to  Type 2 Ho-I was developed in the late  1930s?
Type 2 Ho-I The Type 2 Gun tank Ho-I (二式砲戦車 ホイ , Ni-shiki hōsensha Ho-I ) Support Tank was a derivative of the Type 97 Chi-Ha medium tanks of the Imperial Japanese Army in World War II. Similar in concept to early variant of the German Panzer IV, it was designed as a self-propelled howitzer to provide the close-in fire support for standard Japanese medium tanks with additional firepower against enemy anti-tank fortifications.
Horten Ho 229 The Horten H.IX, RLM designation Ho 229 (or Gotha Go 229 for extensive re-design work done by Gotha to prepare the aircraft for mass production) was a German prototype fighter/bomber initially designed by Reimar and Walter Horten to be built by Gothaer Waggonfabrik late in World War II. It was the first flying wing to be powered by jet engines.