My list of UK philosophers who served in WWI must be expanded to include John Albert Chadwick. I learned of this philosopher from C. D. Broad's obituary for him in Mind. (vol. 49 : 129-131)
Chadwick's main contribution to analytic philosophy is his paper in Mind called 'Logical Constants'. (vol. 36 : 1-11) His other publications included articles, reviews, and discussion notes in Mind. They are chiefly devoted to philosophical logic.
Chadwick was born in Lewes, England (May 23, 1899), to the Rev. Albert Chadwick and Madeleine Ann Chadwick (née Comper). She was born in 1866 in Aberdeen; the father was born in 1863 in Yorkshire.
Broad reports that John Chadwick entered the Special Brigade of the Royal Engineers 'towards the end' of WWI. (Broad, 'John Albert Chadwick: 1899-1939', Mind 49: 129) According to a 'Supplement' to the London Gazette, (June 21, 1918, p. 7291) Chadwick was made (temporarily) a 2nd Lieutenant in the Royal Engineers on May 29, 1918. He seems to have finished the War with that rank. The Special Brigade of the Royal Engineers was formed to handle and release chemical weapons.
After the War, Chadwick began his studies at Cambridge University in 1920. In 1925, he won a fellowship at Trinity College, Cambridge.
Broad writes that the War left 'scars on [Chadwick's] spirit'. (Broad, 129) He adds that Chadwick's early promise in philosophical logic was compromised by a physical illness, the loss of a close friend, and 'another emotional upset' (not further specified). (Broad, 130) According to Broad, the psychological toll exacted by these experiences led Chadwick to become 'aloof from and unreasonably suspicious of many of his colleagues'. (Broad, 130)
Broad says that Chadwick befriended an older couple in Cambridge, John Stuart Mackenzie and Millicent Mackenzie. They were retired academics who devoted much of their time to traveling. J. S. Mackenzie was a respected Hegelian; Millicent Mackenzie, too, was interested in Hegel and had published a book on his philosophy of education. In their retirement, the Mackenzies cultivated an interest in theosophy (which took an interesting form in England) and, in particular, the writings of Rudolf Steiner. They shared with Chadwick an interest in Indian spiritual philosophy.
Via Ancestry.com, I learned that the Mackenzies brought Chadwick along on at least one of their trips. According to the UK Outward Passenger Lists (1890-1960), the three of them departed from Liverpool on July 29, 1926 and traveled 1st-class to Marseilles aboard the Leicestershire. The UK Incoming Passenger Lists (1878-1960) indicate that they returned to England (London) on the Lancashire on Aug. 30, 1926. These two ships originated or terminated their voyages in Rangoon (with stops in Colombo), but the records show that Chadwick and the Mackenzies traveled only as far as Marseilles. All three of the travelers gave their address as being at 2 Hertford St., Cambridge, so Chadwick might have been renting a room in the Mackenzies' house. Strangely, he's identified in the records for the outgoing leg of the trip as a 26-year-old professor but in the records for the return trip (in August) he is a 27-year-old student. (Perhaps he unlearned something in Marseilles.)
In 1927, the Mackenzies helped to secure a teaching position for Chadwick at Lucknow University. (Broad, 130) In 1930, Chadwick resigned his position there and entered the Sri Aurobindo Ashram in Pondicherry, India. He there took the name Arjava and wrote much poetry.
Chadwick's decision to leave the university might have been influenced by a similar choice that had been made by an English professor at Lucknow, Ronald Nixon. Nixon, too, was a WWI vet who studied at Cambridge after the War. He resigned from Lucknow in 1928 and took the name Krishna Prem. (Nixon is among those who is thought to have influenced Somerset Maugham's writing of The Razor's Edge, although the novel's main character might also have been inspired by Major Alan W. Chadwick, yet another English WWI vet seeking enlightenment in India.)
John Albert Chadwick died on May 5, 1939 near Bangalore. He left his money (a little more than £939) to his mother. (England & Wales, National Probate Calendar [Index of Wills and Administrations] 1858-1966)
Update (Oct. 15, 2016): For a small fee, I obtained a copy of J. A. Chadwick's military records from the British National Archives.
According to those records, Chadwick was a student at Marlborough College when he joined the British army. He gave his address as 'Field House, Marlborough College'.
He had been in the Officers Training Corps at Marlborough (from May,
1913 until his enlistment in the army). His attestation papers are dated
Feb. 19, 1917. On May 11, 1917, he applied for admission to an officer
cadet unit, with a preference indicated for the Siege Artillery. His
application includes the signature of his housemaster at Marlborough, C. C. Carter
(later a geography professor at Oxford University), who attested to
Chadwick's moral character. In his application, Chadwick said that he
had never suffered from a 'serious illness or injury', had 'never
suffered from "fits" of any description', and could see well without
needing eyeglasses. His height was 5 ft 9 3/4 inches and he weighed 113
pounds. His application was approved on June 1, 1917.
He was mobilised and posted to the Devonshire Regiment on Dec. 31, 1917. On Jan. 3, 1918, he was attached to 'no. 5' (5th Battalion?) as an officer cadet. He was discharged from the Devonshire Regiment on May 29, 1918 in order to be transferred to the Special Brigade of the Royal Engineers.
The last unit in which he served was the '350th'. His 'theatre of war'
is listed as 'France'. He ceased being paid by the army on Oct. 21,