Tuhia he tomokanga mō tēnei wāhanga - I whakaritea ki te 21st Infantry Regiment, i mahi tuatahi a McAndrew ki te hauauru o te United States, ā, i uru ki te Pakanga Kanikani Wairua ki te Sioux i te tau 1890-1891. I whakatairangahia ia ki te rangatira tuatahi i te tau 1894, a ka tohaina ki te 3rd Infantry. I mahi a McAndrew i Cuba i te Pakanga Paniora-Amerika, a i uru ki te Pakanga o El Caney
me te whakapae o Santiago. I te tau 1899, i whakatairangahia a McAndrew ki te rangatira, a ka mahi ia i nga Philippines i te Pakanga Philippines-American. Mai i te 1905 ki te 1906, i mahi ia me te 3rd Infantry i Skagway, Alaska.