The British were developing pilotless aircraft like the Larynx and the Fairey Queen shortly after WWI. I have noticed that in both world wars the Allies were often taken by surprise after encountering German technology which was actually based on earlier developments (radio/remote control, interruptor gear, oblique gun mountings, etc), often originating in those allied nations.
Query wiki for "Hewitt-Sperry Automatic Airplane" and the "Kettering Bug".