Whakaotihia te rerenga e whai ake nei: I te Pipiri 1861, i whakawhiwhia a O'Neal hei rangatira, a, e toru nga roopu hoia i whakahaua. I te taenga atu ki Richmond i tohua ia hei rangatira o te 9th Regiment Alabama Infantry a i whakatairangahia ia ki te koromatua i te ngahuru. I te Poutu-te-rangi 1862, i tohua ia hei koroneela o te 26th Alabama infantry, a i whakahau i tenei roopu i te Peninsula Campaign. I te Pakanga o Seven Pines, i mate tana hoiho i raro i a ia, a, i whara kinotia ia e tetahi wahi o te pupuhi. I tino whakamoemititia ia mo tana mahi i te Pakanga o Chancellorsville. I te tau 1863, i whakahaua e ia he parirau i roto i te wehenga a Maj. Gen. Robert E. Rodes, a i arahina e ia i te Pakanga o Gettysburg, Pakanga o Manassas Gap me te Pakanga o Roto
Ko te Pakanga o Mine Run. I te timatanga o te tau 1864, i tukuna tana rerenga ki Alabama ki te whakauru i ona rarangi kua pau, engari i whakahaua wawe ki Dalton, Georgia, i reira ka riro a O'Neal i te rangatira o te brigade a Brig. Gen. James Cantey i te Army of Tennessee. I whakahau a O'Neal i tēnei piritiata i te toenga o te pakanga o Atlanta. Whai muri i te whakawhiwhinga o Lieutenant General John Bell Hood ki te whakahau o te Ope Taua o Tennessee, ka tukuna a O'Neal ka mahi i runga i te mahi wehe mo te toenga o te pakanga. I tohua ia hei rangatira pirihimana i te Pipiri 6, 1863, engari i whakamanahia tenei tuunga e Gen. Robert E. Lee a ka whakakorehia te whakatairanga e te Perehitini o te Rōpū Jefferson Davis.