Rubuta ci gaba don wannan sakin layi - Lokacin da yaki ya ɓarke a watan Satumba na 1939, an tattara rukunin kuma an sanya su don kare yankuna masu muhimmanci a kusa da birnin. A cikin 1940 an zaɓi Bataliya ta 1 na rundunar don zuwa ƙasashen waje. Kwanan nan aka sanya Rockingham a matsayin Kyaftin, amma an gaya masa cewa idan yana so ya tafi tare da rundunar ya kamata ya koma matsayinsa na Lieutenant, wanda ya zaɓa ya yi. Bataliya ta yi tafiya zuwa Halifax daga inda suka tashi zuwa Glasgow, kuma ba da daɗewa ba bayan isowa suka koma Aldershot. A can, an nada Rockingham a matsayin kwamandan mai tsaron girmamawa ga Sarki George VI da Sarauniya Elizabeth, waɗanda suka ziyarci wannan Disamba. Daga baya aka tura shi zuwa makarantar kwamandan kamfanin Kanada. Rockingham ya kasance a makarantar lokacin da Kanada ta dauki Dieppe Raid
a ranar 19 ga watan Agusta 1942. An kashe wani ɓangare na Royal Hamilton Light Infantry a lokacin wannan harin, kuma daga bisani aka tura Rockingham zuwa ga rundunar da aka rage a matsayin Major. An kafa shi a kudancin Ingila a matsayin wani ɓangare na rundunar anti-invasion, a ranar 14 ga Afrilu 1943 an ba Rockingham mukamin Laftanar-Colonel kuma ya zama Kwamandan Kwamandan. A ranar 19 ga Fabrairun 1944, an cire Rockingham daga mukaminsa kuma aka tura shi zuwa Kwalejin Staff, Camberley don ƙarin horo. Bayan mamayewar Normandy a ranar 6 ga Yuni 1944, RHLI ya tafi Faransa ba tare da Rockingham ba. Duk da haka, ba da daɗewa ba aka ji rauni. An cire Rockingham daga Kwalejin Ma'aikata, kuma a ranar 18 ga Yuli ya ba da umurnin Rundunar sau ɗaya kuma aka aika zuwa Faransa.