Tuhia he haere tonu mo tenei whitianga - I te Oketopa 1939, i tohua a Mills ki te Tuarua o te Mana Imperial o Ahitereiria ka mahi tahi me te 6th Divisional Reconnaissance Cavalry Regiment. I te Pakanga o Bardia
I te marama o Hanuere 1941 i whakahau ia i nga hoia e toru o nga kaikawe Bren-gun a i whakawhiwhia ki a ia te Karauna o te Hoia mo te maia i te waahi. I te whakaekenga o Hiria i te Pipiri o taua tau i whakawhiwhia ki a ia he Bar ki tana Whawhai Whawhai. Ko Mills te tuatahi o nga hoia Ahitereiria tekau ma rima anake ki te pupuri i taua rereketanga i te Pakanga Tuarua o te Ao. I whakatairangahia ia ki te rangatira i te Hune 1941 me te rangatira i te Hui-tanguru 1942 ana i te Maehe 1943 i whakatairangahia ia ki te koromatua mo te wa poto, ka waiho hei rangatira mo te &lt;a href="2/5th%20Armoured%20Regiment%20%28Australia%29"&gt;2/5th Armoured Regiment&lt;/a&gt;. I te Haratua 1944, i riro a Mills i te &lt;a href="2/4th%20Armoured%20Regiment%20%28Australia%29"&gt;2/4th Armoured Regiment&lt;/a&gt; a i mahi ia ki Madang, New Guinea. I whakarerea e ia te whakahau o te regiment i te Hui-tanguru 1946 ka whakawhiti ki te Reserve o nga Kaimahi i te 27 o Poutu-te-rangi.