Tuhia he haere tonu mo tenei waahanga - I te tau 1900, i whakatairangahia a Ōkubo ki te rangatira rangatira me te rangatira o nga kaimahi o te Inspectorate General of Military Training. I te Haratua 1902, ka riro ia hei rangatira mo te IJA 6th Infantry Division. I te Pakanga a Ruhia-Hapani, i whakauruhia te IJA 6th Infantry Division ki te Rōpū Tuarua o Hapanihi, engari i muri i te Pakanga o Shaho
I whakawhitihia ki te Hapanihi Tuatoru o Hapanihi i mua o te Pakanga o Mukden. Whai muri i te pakanga, i whakawhiwhia ia ki te Order of the Rising Sun, 1st class me te Order of the Golden Kite, 2nd class. I te Hōngongoi 1906, i whakawhitihia ia ki te whakahau i te IJA 3rd Division a i te Mahuru 1907 i whakaarahia ki te "kazoku" peerage me te taitara o "danshaku" (baron).