I te pakarutanga o te Pakanga a-iwi i tohua a Osterhaus hei rangatira o te 2nd Missouri Volunteer Infantry a i te tau tuatahi o te pakanga i whakamahia i Missouri me Arkansas, i reira ia i whai waahi nui ai ki te Pakanga o Wilson's Creek me te Pakanga o Pea Ridge. I Pea Ridge i whakahau ia i nga hoia i whakapiri tuatahi ki nga ope o te Rōpū e ahu whakamua ana i te taha maui o te Uniana. I whakatairangahia ia ki te rangatira rangatira i te Pipiri 9, 1862. I te tau 1863 i whakahau ia i tētahi wehenga i te Pakanga o Port Gibson
, i reira i whakaatuhia ai e ia te pukenga rautaki i roto i te tirotiro i nga kaitautoko Confederate mai i te tuunga pai.