Tuhia he tohutoro mō tēnei wāhanga - I wehe atu a Sneden i Brooklyn i te tau 1861 ki te whakauru ki te 40th New York Volunteer Infantry Regiment, te "Mozart Regiment", o te Army of the Potomac. I mahi ia hei kaitohutohu i te wa i noho ai tana ope ki te taha o Leesburg Turnpike. Mai i te 12 o Hanuere 1862, ka mahi a Sneden ki nga kaimahi o Samuel P. Heintzelman's III Corps, i te tuatahi, hei kaihoahoa i runga i te mahi mahere, i muri mai, hei miihini topographic. I te 22 o Poutu-te-rangi 1862, ka eke a Sneden ki Heintzelman mo te Peninsula Campaign, ka uru ki te Pakanga o Williamsburg, Pakanga o Seven Pines, Pakanga o te Teihana o Savage
, me te Pakanga o Glendale. I tona hokinga ki Northern Virginia, i uru ia ki te Pakanga Tuarua o Bull Run. I whakawhiwhia ia ki nga parenga o Washington, DC, i te tuatahi i Alexandria, Virginia, ka tae ki Arlington House.