 Nyorai kupfuurira kweiyi ndima - Kubva muna 1914 kusvika muna 1915, Chaffee akatumirwa ne7th Cavalry muPhilippines, uye kubva muna 1916 kusvika muna 1917 Captain Chaffee akatumirwa kuWest Point semurairidzi mukuru weCavalry muDhipatimendi reTactical. Apo America yakapinda muHondo Yenyika I muna April 1917, Chaffee akasimudzirwa kwenguva pfupi kuti ave Major uye akapiwa basa semubatsiri we81st Division sezvo yakarongeka paCamp Jackson, South Carolina. Munguva yaMajor Chaffee akashanda semubatsiri weG3 Operations officer muUS IV Corps, uye akazodzokera ku81st Division seG3 panguva yeSt. Mihiel neMuse-Argonnekurwisa. Akasimudzirwa pachigaro chenguva pfupi chaColonel, akava G3, III Corps pakupera kwehondo, uye akagara neuto racho nokuda kwebasa rekugara muna 1919. 