The American professor Robert H. Goddard worked on developing solid-propellant rockets since 1914, and demonstrated a light battlefield rocket to the US Army Signal Corps only five days before the signing of the armistice that ended World War I. He also started developing liquid-propellant rockets in 1921, yet he had not been taken seriously by the public. Nevertheless, Goddard reclusively developed and flew a small liquid-fueled rocket. He developed the technology for 214 patents, 212 of which his wife published after his death.