1. Andrew Thorne served in the First World War, becoming a staff captain, having been promoted to the rank of captain on 22 March 1913, then deputy assistant adjutant and quartermaster general and then deputy assistant quartermaster general in France.
Andrew Thorne became commanding officer of the 3rd Battalion, Grenadier Guards in 1916, and saw action in the First Battle of Ypres in 1914 and Battle of the Somme in 1916, earning the Distinguished Service Order and two Bars.
Andrew Thorne was awarded the Legion of Honour by the President of France in 1917, and was promoted to acting lieutenant colonel in July that year as well.
Andrew Thorne served at the Staff College as an instructor from 1923 to 1925.
Andrew Thorne was appointed military assistant to the Chief of the Imperial General Staff at the War Office in 1925 and commanding officer of the 3rd Battalion, Grenadier Guards again in 1927.
Andrew Thorne was commander of the 1st Guards Brigade at Aldershot Command in 1935, a temporary brigade commander in Palestine and Transjordan in 1936, and in 1938 he became Major General commanding the Brigade of Guards and General Officer Commanding London District.
In 1939, at the start of the Second World War, Andrew Thorne became GOC 48th Infantry Division, which played an important role in the defence of the Dunkirk perimeter in 1940.
Andrew Thorne became GOC Scottish Command and Governor of Edinburgh Castle in 1941 and was appointed a Knight Commander of the Order of the Bath in the 1942 Birthday Honours.
Germany officially surrendered in Norway on 8 May 1945, and Andrew Thorne arrived in Norway on 13 May together with Crown Prince Olav.
Andrew Thorne remained in charge of dismantling the German presence in Norway until he left the country on 31 October 1945.
Andrew Thorne was chairman of the Anglo-Norse Society for some time, and was at some point a deputy lieutenant of Berkshire.