Military career, 1931–1946
Fergusson was educated at Eton College and the Royal Military College, Sandhurst. From the latter, he was commissioned as a second lieutenant into the Black Watch on 27 August 1931. He served with the 2nd Battalion of his regiment in the British Mandate of Palestine during the Arab revolt and later became aide-de-camp (ADC) to Major General Archibald Wavell, then General Officer Commanding the 2nd Infantry Division in England, on 11 March 1937. At the outbreak of the Second World War, he was on the Directing Staff at the Royal Military Academy, Sandhurst.
In 1940, Fergusson was serving as a brigade major for the 46th Infantry Brigade before becoming a general staff officer in the Middle East, where he also saw active service with Free French forces in Syria and with the Black Watch in Tobruk. In 1942 he served briefly in the Joint Planning Staff in Delhi, before transferring to Orde Wingate's embryonic Chindit force experimenting with Long Range Penetration campaigns. He commanded No. 5 Column in Wingate's 1943 campaign (Operation Longcloth) in Japanese-occupied Burma, for which he was appointed a Companion of the Distinguished Service Order (DSO). In October 1943 he was promoted to acting brigadier and given command of the 16th Infantry Brigade, which was converted into a Chindit formation for operations in the deep jungles of Burma miles behind Japanese lines. He commanded this brigade throughout the Chindit operations of 1944 (Operation Thursday). 16 Brigade, alone of the Chindit brigades, went into Burma on foot in a five week march through very difficult terrain. He established a stronghold, "Aberdeen", in keeping with Wingate's strategic vision and led an unsuccessful assault on the airfields at Indaw before his Brigade was flown out. He was Director of Combined Operations from 1945 to 1946.
He wrote about both Burma campaigns in Beyond the Chindwin and The Wild Green Earth and stood unsuccessfully for Parliament in the 1945 election.
