Watson transferred to the
Australian Flying Corps in 1917, and was trained in England. On 5 February 1918, he was assigned to 4 Squadron AFC as a
Sopwith Camel pilot. He drove an
Albatros D.V down out of control for his first victory, on 19 April 1918. He steadily accumulated triumphs, shooting down eight aircraft by the end of June. Watson was subsequently awarded the
Distinguished Flying Cross (DFC) in mid-July. His final tally was three enemy observation balloons destroyed, including one set afire; four enemy fighters destroyed; an enemy observation plane destroyed in conjunction with Lieutenant
Elwyn King; four enemy fighters and an observation plane driven down out of control. As he completed his string of wins, he was appointed a flight commander with the rank of captain. ==After World War I==