Brown set sail for England on 22 November 1914 and underwent further training at
Chingford Aerodrome. On 2 May 1916, Brown crashed his
Avro 504 emerging apparently unscathed, though next morning he experienced severe back pain as he had broken a
vertebra. He spent two months in hospital and in September 1916 was posted to
Eastchurch Gunnery School. In January 1917, he was sent to
Cranwell to complete advanced training. In March 1917, Brown was posted to
No. 9 Naval Squadron, flying coastal patrols off the Belgian coast in
Sopwith Pups. In April, "B" Flight, which included Brown, was attached to the Army's
Royal Flying Corps to assist during the
Battle of Arras. Brown fell ill at this time and missed "
Bloody April", a period when British casualties were very high. In June 1917, Brown was posted to
No. 11 Naval Squadron, and in July he was briefly posted to No. 4 Naval Squadron before returning to No. 11 Naval Squadron later that month. On 17 July, he achieved his first "kill", an
Albatros D.III, while flying a Pup, and gathered another three unconfirmed kills. No. 11 was disbanded in mid-August 1917, and Brown returned to No. 9, equipped with the
Sopwith Camel. He was promoted to
flight lieutenant on 1 October, and on 6 October, Brown was awarded the
Distinguished Service Cross (DSC). His citation read: Soon after, Brown was made a
flight commander, a role in which he excelled. No. 9 was posted to the
Somme area in early 1918, and was forced to retreat during the
German spring offensive between 20 and 29 March. The tempo of operations increased, with the entire squadron typically flying two missions a day. Colonel
Raymond Collishaw noted on an April visit that Brown looked exhausted: he had lost , his hair was prematurely turning grey, and his eyes were bloodshot and sunken. Also eating contaminated rabbit had left him severely sickened with
gastritis. Against Collishaw's suggestions, Brown refused to quit flying, and shot down another two aircraft on 11 and 12 April. On 1 April 1918, the RFC and RNAS were merged into the
Royal Air Force. Brown's No. 9 Squadron RNAS became No. 209 Squadron RAF. ==Fighting the Red Baron==