Rubuta ci gaba don wannan sakin layi - A lokacin Yaƙin Duniya na II, ya umurci rundunar bindigogi. Ya jagoranci bindigogi a ƙasashen waje yayin mamayewar Allied na Sicily a watan Yuli-Agusta 1943, inda ya sami na farko na Gicciye Biyu na Musamman. Ya ci gaba da jagorantar bindigogi a cikin mamayewar Allied na Italiya a watan Satumba, kuma a farkon matakan yakin Italiya, kafin a tura shi zuwa Ingila. A lokacin yakin Normandy a watan Agustan 1944, McLain ya dauki umurnin 90th Infantry Division, wanda ke da matsaloli masu yawa. McLain ya canza 90th zuwa wani nau'i na farko, kuma ya jagoranci shi a fadin Faransa a cikin Allied gaba daga Paris zuwa Rhine
kuma a cikin yaƙe-yaƙe da yawa da yawa a Yammacin Yamma. A watan Oktoba sai ya karbi umurnin XIX Corps, ya kasance kwamandansa har zuwa karshen yakin. Shi ne kawai mai tsaron gida wanda ya jagoranci rundunar soja a lokacin yakin duniya na biyu.