original_query: When did Lieutenant Colonel Spencer Bertram Horn serve in the Dragoon Guards regiment?
query: When did Lieutenant Colonel Spencer Bertram Horn serve in the Dragoon Guards regiment?
answer: He was commissioned into the 3rd (Prince of Wales's) Dragoon Guards on October 1, 1914.  He returned to the regiment after WWI in December 1919 and served in it until at least 1944 (when he was still Lieutenant-Colonel in command of the 3rd Carabiniers, successor to the 3rd Dragoon Guards).