Question: The historical unit of the US Army that began its service before the Civil War fought in what battle in 1879?

Context paragraphs:
Eric J. Wittenberg: Eric J. Wittenberg (born March 26, 1961) is an American Civil War (Civil War) historian, author, lecturer, tour guide and battlefield preservationist.  He is a practicing attorney in downtown Columbus, Ohio.  His published works have focused especially on the Civil War cavalryman and the cavalry battles of the Civil War, with emphasis on the Army of the Potomac's Cavalry Corps.  His first book, "Gettysburg's Forgotten Cavalry Actions", was chosen as the best new work addressing the Battle of Gettysburg in 1998, winning the Robert E. Lee Civil War Roundtable of Central New Jersey's Bachelder-Coddington Award.  The second edition of this book, published in 2011, won the U. S. Army Historical Foundation's Distinguished Writing Award for that year's best reprint.  In 2015, his book "The Devil's to Pay: John Buford at Gettysburg" won the Gettysburg Civil War Roundtable's 2015 Book Award.  He was a member of the Governor of Ohio’s Advisory Commission on the Sesquicentennial of the Civil War and has been active with several Civil War battlefield preservation organizations.  He and his wife Susan Skilken Wittenberg reside on the east side of Columbus, Ohio.

Charles L. Pyron: Charles Lynn Pyron (1819–1869) was a soldier in the United States Army in the Mexican-American War and a Confederate Army officer in the American Civil War.  He fought at the Battle of Monterrey in the Mexican-American War, and during the Civil War fought in the West, including at the battles of Valverde and Glorieta Pass.

5th Cavalry Regiment: The 5th Cavalry Regiment ("Black Knights") is a historical unit of the United States Army that began its service in the decade prior to the American Civil War and continues in modified organizational format in the U.S. Army.

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.  He was among 10 cavalrymen who volunteered to form a skirmish line on September 29, 1879 while Company D retreated from an attack by the White River Utes.  Philipsen and the other volunteers were awarded the Medal of Honor for bravery in defending their unit during this retreat.

Battle of Pine Island Ridge: The Battle of Pine Island Ridge was a battle during the Second Seminole War fought on March 22, 1838 at the site of what is now Pine Island Ridge, Florida.  According to US Army accounts, Major William Lauderdale surprised the Indians and drove them off Pine Island, which was an island in the Everglades at the time.  However Seminole claim that scouts posted around the island had already alerted the Indians, allowing them to successfully evacuate the island.

Kenneth Bowra: Kenneth Bowra is a retired major general who served in the US Army from 1970 to 2003.  Bowra saw service with US special forces in the Vietnam War and Cambodian Civil War and has worked with the Central Intelligence Agency and Joint Special Operations Command.  He later fought in the US Invasion of Grenada and in the Somali Civil War and First Gulf War.  In 1998 he was given command of the John F. Kennedy Special Warfare Center and School and in 2000 was deputy commander of NATO's Kosovo Force.  Retiring in 2003 he is now a diplomat with the US State Department in Saudi Arabia.

Coats of arms of U.S. Army units: Coats of arms of US Army units are heraldic emblems associated with units in the US Army.  Under Army Regulation 840-10, each regiment and separate table of organization and equipment (TOE) battalion of the US Army is authorized a coat of arms to be displayed on the organization's flag, called the "colors."  This coat of arms usually forms the basis for the unit's distinctive unit insignia (DUI), the emblem worn by all members of the unit on their service uniforms.

Wilfred C. Menard, Jr.: Maj. Gen. Wilfred Charles Menard, Jr. (November 10, 1918 – February 20, 2012) (ARNG) was the twenty-sixth Adjutant General of New Jersey.  Commissioned a US Army 2nd lieutenant in 1942, he served actively with the Army during the Second World War rising to the rank of US Army captain.  He continued to serve thereafter as a reserve officer in the New Jersey Army National Guard, which he commanded from 1974-1982.  A graduate of the United States Army Field Artillery School, the United States Army Tank Destroyer School, and the United States Army War College, Menard was an experienced artillery officer.  During his service with the Guard, he was briefly reactivated at the rank of Lieutenant Colonel for the Berlin Crisis of 1961.  Born in Trenton, NJ, Maj. Gen. Menard was a lifelong resident of central New Jersey.  His many military awards and decorations include the Distinguished Service Medal (US Army) and the Legion of Merit.

Mohammed Kahn: Mohammed Kahn or John Ammahail (b. 1830) was a Persian-born American soldier in the American Civil War, who was enlisted as a private in the 43rd New York Infantry and fought at the Battle of Gettysburg.  Born in Persia and raised in Afghanistan he migrated to the US in 1861, where he soon enlisted after encouragement from some friends.  After having fought in the Battle of Gettysburg he was separated from his unit as a Union guard arrested him because he didn't believe that non-White Kahn could really be serving in the 43rd Infantry which was a white unit.  After his release a few days later he managed to jump a southbound train to D.C. where he rejoined his unit on the last day of the Battle of the Wilderness, where he was wounded.  He spent the rest of the war as a sharpshooter, and applied for an army pension which was approved in 1881.  He is one of a small number of Muslims who served in the American Civil War, and is known primarily from his pension application which is housed at the US National Archives

Battle of Tashan: The Battle of Tashan () was a battle during the Chinese Civil War fought in the western part of Northeast China, between forces of the Kuomintang National Revolutionary Army (NRA) and the communist People's Liberation Army (PLA), and resulted in a PLA victory.  The battle was critical in determining the outcome of the Battle of Jinzhou and, consequently, that of the entire Liaoshen Campaign.  The battle is more commonly known as the blocking battle at Tashan (), and is widely regarded by the communists as the first of the three most crucial blocking operations (along with the Battle of Heishan a week later and the Battle of Xudong from the Huaihai Campaign) during the Chinese Civil War.

Supporting paragraphs: Wilhelm O. Philipsen 5th Cavalry Regiment
Answer: Battle of Milk Creek