Ka cika wannan jumla: Sneden ya bar Brooklyn a shekara ta 1861 don ya shiga cikin rundunar New York Volunteer Infantry Regiment, ko kuma "Mozart Regiment", na Sojojin Potomac. Ya yi aiki a matsayin mai kula da lokacin da rundunarsa ta yi zango a kusa da Leesburg Turnpike. Farawa daga Janairu 12, 1862, Sneden ya yi aiki a kan ma'aikatan Samuel P. Heintzelman na III Corps, da farko, a matsayin mai zane a kan aikin taswira, daga baya, a matsayin injiniyan topographical. A ranar 22 ga Maris, 1862, Sneden ya shiga tare da Heintzelman don Kamfen na Peninsula, yana shiga cikin Yaƙin Williamsburg, Yaƙin Bakwai Bakwai,
Yaƙin Tashar Savage, da Yaƙin Glendale. Komawa zuwa Arewacin Virginia, ya shiga cikin yakin na biyu na Bull Run. An ba shi izinin kare Washington, DC, da farko a Alexandria, Virginia, sa'an nan kuma a Arlington House.