Kammala jumla mai zuwa: McRae an umurce shi a cikin Rundunar Sojoji ta Uku kuma ya yi aikin aikin iyaka daga 1886-1888. A lokacin yakin Spain-Amurka, ya kasance a cikin
Ya kuma yi aiki a cikin Sanitary Corps, wanda ya sami lambar yabo ta farko ta Silver Star. Ya karɓi tauraron Azurfa na biyu a lokacin Tashin hankali na Philippine kuma an ba shi shawarar don haɓakawa. Daga 1905 zuwa 1908, ya yi aiki a kan Janar Janar, kuma a 1911, ya sauke karatu daga Kwalejin War Army na Amurka. McRae ya yi aiki a Ma'aikatar Janar daga 1913 zuwa 1917, kuma a ranar 5 ga Agusta, 1917, an ba shi mukamin brigadier general kuma ya umurci Brigade na 158 a Camp Sherman, Ohio. Bugu da kari, ya umurci Brigade na Tara na Rundunar Sojoji ta Biyar. An gabatar da shi zuwa babban janar a ranar 12 ga Afrilu, 1918, kuma ya umurci rundunar soja ta 78 (AEF) har zuwa Yuni 1919, lokacin da aka kashe shi. Don wannan, ya sami lambar yabo ta musamman. A lokacin 1921 da 1922, shi ne mataimakin shugaban, G-1 (ma'aikata).