Tuhia he tohutoro mō tēnei whārangi - I te tīmatanga o te Pakanga Tuatahi o te Ao i te tau 1914, ka haere a Jacob ki te wāhanga o Meerut, he wāhanga o te rōpū Inia, ki te Rāwhiti o te Uru. I kite ia i te mahi i nga waahanga whakamutunga o te Pakanga o La Bassée
i te Oketopa o te tau 1914. I whakatairangahia ia ki te brigadier-general mo te wa poto i te 5 o Hanuere 1915, i tohua ia hei rangatira mo te Dehra Dun Brigade, a i arahi ia i te brigade i te Pakanga o Neuve Chapelle i te Poutu-te-rangi 1915 me te Pakanga o Aubers Ridge i Mei 1915. I whakatairangahia ia ki te rangatira rangatira mo te wa poto i te 7 o Hepetema 1915, ka riro ia hei Kaiwhakahaere Matua e whakahau ana i te wehenga o Meerut ka arahi i te wehenga i te Pakanga o Loos i te Oketopa 1915. I a ia e whakareri ana te Indian Corps ki te wehe i te taha ki te Hauauru, i tohua ia ki te tango i te 21st Division o te "New Armies" i te 18 o Noema 1915. I whakatairangahia ia ki te taumata matua o te rangatira nui i te 1 o Hanuere 1916 a ahakoa i whara ia i te Maehe 1916, i whakatairangahia ia ki te rangatira rangatira mo te wa poto i te 28 o Mei 1916 ka tohua hei rangatira mo te II Corps i te Fifth Army i te marama o Hepetema 1916. I te Pakanga o te Somme, i whakaekea e tana roopu te whakaeke a Ingarangi i te Pakanga o Thiepval Ridge i te marama o Hepetema 1916 me te whakaekenga o St Pierre Divion i te Pakanga o te Ancre i te marama o Noema 1916. I noho tonu ia hei rangatira mo te II Corps, i te mea i whakatairangahia ia ki te taumata rangatira o te lieutenant-general i te 3 o Hune 1917, mo te Pakanga o Passchendaele i te ngahuru 1917.