Question: The historical unit of the US Army that began its service before the Civil War fought in what battle in 1879?
Sentence (from "Wilhelm O. Philipsen"): Wilhelm O. Philipsen (1852–1913), a recipient of the Medal of Honor, served as a blacksmith in Company D of the U.S. Army’s 5th Cavalry Regiment during the Battle of Milk Creek in 1879.
Relevant evidence: Yes