Kammala jumla mai zuwa: Colley-Priest ya shiga cikin 8th Field Ambulance, wani ɓangare na 8th Infantry Brigade na Australian Imperial Force, a ranar 19 ga Mayu 1915 kuma ya hau jirgin HMAT Ascanius a ranar 9 ga Nuwamba, zuwa Masar da Yammacin Yamma. Yayin da yake aiki, an tura shi Somme, Racquinghem, Polygon Wood, Messines,
Villers-Bretonneux da kuma Mont Saint-Quentin. A cikin 1917, an ba Colley-Priest lambar yabo ta Soja. Shawarar don kyautar ta lura cewa ya nuna: