* In 1862, after the American Civil War raged for a year, Barney joined the 7th New York Militia Regiment (Company F) as a Private for 90-day service 
* In October he joined the 68th New York Infantry Regiment (Company G). 68th was part of the Army of the Potomac's XI Corps
* A month later Barney, who was listed in some rosters as ''John Barney'', was commissioned a 1st Lieutenant.
* February 1864 Barney was promoted to Captain and assigned to the staff of General Rufus Saxton. He functioned as an Assistant-Adjutant General to the forces stationed in South Carolina.
* During summer he was offered the colonelcy of the 106th New York Infantry Regiment, but he declined. Instead he tried to raise the 180th New York Infantry. February 1865 the 180th regiment was disorganized and the men transferred to the 179th New York
* On March 13, 1865, (aged 20) he was brevetted both Brigadier and Major General of the U.S. Volunteers
* After the war Barney settled in California and married his wife, Mary S. Fowler, in 1875. He died in Inglewood on December 19, 1904; and is buried on Rosedale Cemetery, Los Angeles (now Angelus-Rosedale Cemetery).
Sources noted on wikipedia page. More details there.