Rubuta ci gaba ga wannan sakin layi - A lokacin Latimer na shekara ta biyu na karatu, yakin basasa ya ɓarke kuma Latimer ya bar VMI don bauta wa Kudancin Kudancin. Ya fara aiki ne a matsayin mai horar da 'yan makaranta na Richmond Hampden Artillery a lokacin bazara da lokacin rani na 1861. A cikin fall, an ba shi izini a matsayin mai ba da shawara na farko kuma ya ga aikin tare da Maj. Janar Richard S. Ewell a cikin Kamfanin Shenandoah Valley na 1862. Bayan da ya yi fice da batirinsa a irin wannan yakin kamar Winchester na farko
da Cedar Mountain, Latimer ya ci gaba da zama kwamandan battalion wanda ya kasance na A. R. Courtney. Bayan ya umurci rundunar a Fredericksburg a watan Disamba na 1862, Latimer ya ci gaba da zama babban jami'in a watan Maris na 1863. Ewell ya kira shi "Saurayi Napoleon", amma abokan zamaninsa sun lura da ƙuruciyarsa da ƙarami, ƙarancin girma ta hanyar kiran shi "Boy Major". Ya zama jami'i a cikin Maj. Richard Snowden Andrews na Battalion na Maj. Janar Edward "Allegheny" Johnson na Division.