Green began his military service with the
164th (Halton and Dufferin) Battalion, CEF, with whom he enlisted. He transferred to the
Royal Flying Corps, and was rated as a
Flying Officer while still a
lieutenant, on December 22, 1917. He was stationed in
Salonika, Greece with B Flight of 47 Squadron as a pilot of
Royal Aircraft Factory SE.5as. On April 13, 1918, he and fellow Canadian
Gerald Gordon Bell destroyed an enemy
Albatros D.III. When 47 Squadron's fighter flights were incorporated into forming the newly 150 Squadron, Green went with them. On May 6, he began a string of ten triumphs with his new squadron by driving down a
DFW reconnaissance foe. He accrued victories one or two at a time until July 18, 1918. By then, he had destroyed six enemy planes, including the one shared with Bell and another shared with
Acheson Goulding. He had also driven down five other opponents out of control. ==Post World War I==