A graduate of Eton College and the Royal Military Academy Woolwich, Adam was commissioned on 27 July 1905 into the Royal Artillery. After a posting to India with the Royal Horse Artillery, he served on the Western Front and the Italian Front during the First World War. After the war he attended the Staff College, Camberley, and held successively senior staff postings at the War Office. He was an instructor at the Staff College between 1932 and 1935, and was briefly its commandant in 1937. When Lord Gort became CIGS, Adam was made Deputy Chief of the Imperial General Staff (DCIGS). In October 1939, he was appointed commander of III Corps. When, in late May 1940, the BEF was ordered to evacuate France, Adam was given the task of organising the Dunkirk perimeter. Following his return from France on 31 May 1940, Adam was appointed General Officer Commanding-in-Chief Northern Command, responsible for the defence of the coastline from The Wash to the Scottish border.