Myles Walter Keogh was an Irish soldier. He served in the armies of the Papal States during the war for Italian unification in 1860, and was recruited into the Union Army during the American Civil War, serving as a cavalry officer, particularly under Brig. Gen. John Buford during the Gettysburg Campaign and the three-day Battle of Gettysburg. After the war, Keogh remained in the regular United States Army as commander of I Troop of the 7th Cavalry Regiment under George Armstrong Custer during the Indian Wars, until he was killed along with Custer and all five of the companies directly under Custer's command at the Battle of the Little Bighorn in 1876.

The 7th Cavalry Regiment is a United States Army cavalry regiment formed in 1866. Its official nickname is "Garryowen", after the Irish air "Garryowen" that was adopted as its march tune. The regiment participated in some of the largest battles of the Indian Wars, including its famous defeat at the Battle of Little Bighorn, where its commander Lieutenant Colonel George A. Custer was killed.