I knew about early experimental jet aircraft such as the British Gloster E.28/39 and the German Heinkel He 178, but I didn't know that Italy also developed a "sort-of-jet" aircraft - the Caproni Campini N.1. Wikipedia describes its propulsion as follows.
As designed by Campini, the aircraft did not have a jet engine in the sense that we know them today. Rather, a conventional 900 hp (670 kW) Isotta Fraschini L.121 RC.40 12-cylinder liquid-cooled piston engine was used to drive a three-stage variable-incidence compressor, which forced air into a combustion chamber where it was mixed with fuel and ignited. The exhaust produced by this combustion was to drive the aircraft forward. Campini called this configuration a "thermojet," but the term "motorjet" is in common usage today. It has also been described as a ducted fan.
Here's film of the Campini N.1's development and trials.
There's only one prototype still in existence, in an Italian museum. I'd love to see it sometime.