Kammala jumla mai zuwa: Bayan barin Alabama tare da ƙaramin ƙarfinsa, an ba Reno izinin ɗan lokaci don ya jagoranci Fort Leavenworth Arsenal har sai an nada shi brigadier janar na masu sa kai a cikin kaka na 1861. An canja shi zuwa Virginia, ya dauki umurnin Brigade na 2, Burnside Expeditionary Force, kuma nan da nan ya shirya ƙungiyoyi biyar. Rundunar ta 2 ta yi yaƙi a Maj. Janar Ambrose Burnside na Arewacin Carolina Expedition daga Fabrairu zuwa Yuli 1862. Reno ya zama kwamandan kwamandan a cikin IX Corps, wanda ya zama wani ɓangare na Army of the Potomac. A cikin Yakin Arewacin Virginia, Reno ya yi tsayayya da abokinsa da abokin aikinsa Stonewall Jackson a lokacin Yaƙin Bull Run na biyu da kuma
Yaƙin Chantilly. An nada Reno a matsayin babban janar a ranar 20 ga Agusta, 1862. (An tabbatar da wannan ci gaba a ranar 9 ga Maris, 1863, tare da ranar da aka kafa shi a ranar 18 ga Yuli, 1862.) Burnside ya zama kwamandan rundunar sojojin Potomac na dama don fara yakin Maryland a watan Satumba, ya daukaka Reno zuwa umurnin IX Corps daga Satumba 3.