Tulis hiji continuation for this paragraph - Dina 1860, Parnell anjog di Amérika Sarikat sarta ngagabung jeung Angkatan Darat AS di Brooklyn, New York nalika Perang Sipil Amérika mimiti taun saterusna. Manéhna jadi anggota 4th Regiment New York Volunteer Cavalry, nu dipikawanoh minangka "Dickel's Mounted Rifles", nu utamana ngawula jeung Army of the Potomac. Salila dua taun mimiti perang, manéhna jadi bagian tina kampanye Kolonel Louis Blenker di Lembah Shenandoah jeung Virginia Kulon. Manéhna ogé milu dina patempuran Cross Keys, Port Republic, Cedar Mountain, jeung Second Battle of Bull Run. Kalayan Korps Kavaleri, manéhna ogé tarung dina patempuran Fredericksburg, Beverly Ford, Brandy Station, Stoneman's Raid, Aldie, jeung Middleburg. Tanggal 21 Juni 1863, manéhna direbut sanggeus mingpin serangan kavaleri nu gagal dina Patempuran Upperville jeung sakeudeung ditahan salaku tawanan perang. Anjeunna kabur dua bulan saterusna sarta indit ka Petersburg, Virginia Kulon dimana anjeunna patepung deui jeung resimen na. Manéhna saterusna ngalaman aksi di Patempuran Wilderness, Spotsylvania, Stasion Trevilian, Petersburg, Lee's Mills, Winchester
jeung Cedar Creek diantara kalibet séjénna.