Rubuta ci gaba ga wannan sakin layi - A daren 8 ga Afrilu 1917, yayin da aka fara yakin Arras, Bataliya ta 10 ta kai hari kan Louverval Wood, wani sansanin da ke Hindenburg Line na tsaron Jamus. McCann ya ji rauni a wuyansa a lokacin harin, kuma bayan da aka ɗaure shi kuma ba shi da ikon yin magana, ya kasance tare da sojojinsa har tsawon sa'o'i, kuma bisa ga "Kamfanin Australiya na Tarihin Rayuwa", "ya kasance wahayi ga mutanensa". Da zarar yanayin ya bayyana, sai ya nemi kulawar likita kuma aka kai shi asibiti a Ingila. Bayan makonni shida na farfadowa, McCann ya koma ƙungiyarsa a ƙarshen Mayu, yana ɗaukar umurnin A Company. Ya kasance tare da bataliya a duk lokacin yakin Passchendaele a Flanders daga Yuli zuwa Nuwamba 1917, gami da yakin Menin Road Ridge
a watan Satumba, kafin a tura shi zuwa wani rukunin horarwa a Burtaniya a karshen watan Disamba. Ya koma rundunarsa a watan Yuni 1918. A ranar 29 ga watan Yuni, bayan da bataliya ta kama wani ɓangare na Jamus ta amfani da dabarun "saukewa cikin lumana", kamfanin McCann ya kasance a cikin sabon matsayi lokacin da Jamus suka kai hari kuma suka shiga tsakanin matsayinsa na gaba. Ya jagoranci kamfanoninsa, manzanni da kuma ajiyar ajiyar gaba a cikin rata. 'Yan Jamus sun watsar da makaman su, wanda ya hada da bindiga, kuma ya gudu.