United States army officer, was born in Ireland and moved to New York at an early age. On July 24, 1862, he was commissioned a first lieutenant and appointed adjutant of the 163d New York Infantry. He left the regiment on December 11, 1862, but on February 24, 1864, was appointed colonel of the Eighteenth New York Cavalry. As a member of Maj. Gen. Nathaniel P. Banks's Army of the Gulf, he saw extensive action in Louisiana during the Red River campaign of 1864. Byrne was brevetted to brigadier general for gallantry at the battles of Pleasant Hill and to major general for his conduct at the battles of Moore's Plantation (May 5-6, 1864) and Yellow Bayou (May 18, 1864), both brevets being issued on March 13, 1865. According to a report in the Fort Worth Democrat (see FORT WORTH STAR-TELEGRAM), he was the youngest general in the United States Army. He was mustered out of volunteer service 5/3/1866. 

Was killed by an attack by the Apache Victorio and buried near Fort Quitman but later re-interred in Fort Worth 1880.