Kammala jumla mai zuwa: An sanya shi zuwa Rundunar Sojoji ta 21, McAndrew ya fara aiki a yammacin Amurka, kuma ya shiga cikin Yakin Gidan Gidan Gidan Gida na Sioux a 1890<unk>1891. An ci gaba da shi zuwa na farko a shekara ta 1894, kuma an sanya shi zuwa 3rd Infantry. McAndrew ya yi aiki a Cuba a lokacin yakin Spain da Amurka, kuma ya shiga cikin
Yaƙin El Caney da Siege na Santiago. A shekara ta 1899, an daukaka McAndrew zuwa kyaftin, kuma ya yi aiki a Philippines a lokacin Philippine-American War. Daga 1905 zuwa 1906, ya yi aiki tare da 3rd Infantry a Skagway, Alaska.