Kammala jumla mai zuwa: Daga 1942<unk>1946, a lokacin Yaƙin Duniya na II, McKeithen ya yi aiki a matsayin laftanan farko a cikin Rundunar Sojojin Amurka ta 77 a cikin Pacific Theater of Operations. Ya yi yaƙi a yaƙin Guam,
Tekun Leyte, Ie Shima, da Okinawa. An ba shi lambar yabo ta Bronze Star guda biyu da kuma Gicciye na Musamman.