[2] Several of his fellow classmates included future general officers, such as Charles Pelot Summerall, Tracy Campbell Dickson, Julian Robert Lindsey, William Ruthven Smith, James Ancil Shipton, Louis Chapin Covell, Preston Brown, George Blakely, John M. Palmer, Frank W. Coe, Howard Russell Hickok, Robert Mearns, Henry Howard Whitney, William Chamberlaine, John E. Woodward and Peter Weimer Davison.

Barnhardt was commissioned a second lieutenant in the Sixth Cavalry and served at Fort McKinney, New York, from September 30, 1892, to October 2, 1894.

From 1921 to 1925, after arriving back in the United States, Barnhardt was a General Staff colonel, and from 1925 to 1927 he commanded the Sixth Cavalry.

[2] Barnhardt was awarded the Distinguished Service Medal from the United States, as well as the Croix de Guerre with Palm and the Legion of Honor (Officer) from France.

He repeatedly displayed superior tactical judgment, and by his exceptional ability, leadership, and devotion to duty, he effectively executed the most difficult missions assigned to his regiment.