Born on 2 December 1877, William Thomson was the fourth son of Captain William Thomson of the 78th Highlanders and Alice Broughton. His older brother was Henry Broughton Thomson; Gwyneth Bebb married another brother, Thomas Weldon Thomson. He was educated at Bedford School.[1]
On 16 November 1918, in Bandar-e Anzali, Thomson met with Nasib Yusifbeyli, Musa bey Rafiyev and Ahmet Ağaoğlu, representatives of Musavat, the governing party of the Azerbaijan Democratic Republic (ADR). He outlined his goals as (i) ensuring the evacuation of military units of the Ottoman Army and the ADR from Baku, (ii) preventing Armenian troops from entering Baku, (iii) creating a British administration of local militia, (iv) facilitating the supply of oil from the Baku oilfields for the British, and (v) securing the eastern terminus of the Transcaucasus Railway. He denied that the British would interfere in internal affairs: "The principle of self-determination of peoples decided at the Paris Peace Conference from which Azerbaijan will not be excluded".[2]
Thomson arrived in Baku the next day with about 2,000 soldiers of the British Indian Army and a detachment of Russian troops commanded by Nikolai Baratov. This was greeted with enthusiasm by the Russians of Baku. One of Thomson's first actions was to order the removal of the flag of the ADR. He also spoke in praise of Russia, declaring "The Allies cannot return home without restoring order in Russia and placing her in a position to again take her proper place among the nations of the world."[3]
Thomson went on to become commander of the 154th Infantry Brigade in April 1920, General Officer Commanding the Presidency and Assam District in November 1924 and General Officer Commanding the 51st (Highland) Division in June 1925.[4]
Thomson retired from the British Army in 1934. He was given the Colonelcy of the Seaforth Highlanders in 1939, holding the position until 1947.[5]
He died on 23 July 1963. He is buried in Kinloss Abbey but is also memorialised on a family stone within the eastern enclosure at St Machar's Cathedral.[1]