Kammala jumla mai zuwa: A watan Oktoba na 1939, an nada Mills zuwa Rundunar Sojoji ta Australiya ta Biyu kuma ta yi aiki tare da Rundunar Sojojin Sojojin Sojoji ta 6. A cikin
Yaƙin Bardia a watan Janairun 1941 ya umurci sojoji uku na masu dauke da bindigogi na Bren kuma an ba shi Gicciye na Soja don jaruntaka a fagen. A lokacin mamayewar Siriya a watan Yunin wannan shekarar an ba shi lambar yabo ta Bar zuwa Gicciye na Soja. Mills shine na farko daga cikin sojoji goma sha biyar na Australiya da suka riƙe wannan bambanci a Yaƙin Duniya na II. An daukaka shi zuwa kyaftin a watan Yunin 1941 kuma Manjo a watan Fabrairun 1942 kuma a watan Maris na shekarar 1943 an daukaka shi zuwa laftanan Kanal na wucin gadi kuma ya zama kwamandan rundunar sojan ruwa ta 2/5th. A watan Mayu 1944, Mills ya dauki umurnin na &lt;a href="2/4th%20Armoured%20Regiment%20%28Australia%29"&gt;2/4th Armoured Regiment&lt;/a&gt; kuma ya yi aiki a Madang, New Guinea. Ya yi murabus daga umurnin rundunar a watan Fabrairun 1946 kuma an tura shi zuwa Rukunin Jami'ai a ranar 27 ga Maris.