Kammala jumla mai zuwa: A watan Agusta 1917, Gatley ya ci gaba da zama brigadier janar a matsayin kwamandan na 55th Field Artillery Brigade, wani sashi na 30th Division. Daga bisani an canza shi zuwa umurnin Brigade na 67 na Artillery Brigade na 42nd Division, wanda ya jagoranci har zuwa karshen yakin. Ya shiga cikin
Champagne-Marne, Aisne-Marne, St. Mihiel, da kuma Meuse-Argonne fadace-fadace da hare-hare. Daga Disamba 1917 zuwa Janairu 1918, Gatley ya jagoranci rundunar ta 30. A cikin 1919 ya umurci Rukunin na 42 a lokacin wani ɓangare na aikinsa na bayan yaƙin a Jamus.