Tuhia he tomokanga mo tenei whitianga - I muri i nga tau e ono i te rahui ope taua me te Horse Maama o Ahitereiria, ka uru a Green ki te ope taua i te pakarutanga o te Pakanga Tuatahi o te Ao ka eke hei kaiawhina i te 6th Light Horse Regiment i runga i te "Suevic" i te 21 o Tihema 1914. I mahi ia i Ihipa, i te Pakanga o Gallipoli me te Runga Hauauru; kotahi te pupuhi i a ia i Gallipoli, i ora mai me te noho roa ki te hohipera ka hoki ki Ahitereiria i te tau 1916, i mua i te hokinga mai i te marama o Noema 1916. I mahi ia tae noa ki te whara ano i te wa i ngaro ai tona waewae i te Pakanga o Menin Road
i Belgium, i te marama o Hepetema 1917. I hoki ia ki Ahitereiria i te 30 Pipiri 1918 ka hoki ki tana pāmu i Woolomin. Ko ia te kaiwhakaara me te perehitini tuarua tuatahi o te Limbless and Maimed Soldiers 'Association, he mema o te Poari Tiaki Tamworth Pastures, a he kaitono kore angitu a Progressive Party i te pooti kawanatanga o te tau 1922.