At the outset of the Civil War, Kelly enlisted in the Union Army and saw action as
captain of Company E of the
69th New York Infantry at the
First Battle of Bull Run. He briefly was a captain in the
16th U.S. Infantry. On September 14, 1861, he was named
lieutenant colonel of the
88th New York Infantry and fought in the Irish Brigade's major battles in 1862. He commanded the regiment at the
Battle of Antietam. While stationed at
Harpers Ferry following the
Maryland Campaign, he was promoted to
colonel on October 20, 1862. He led the regiment in the ill-fated attacks in front of Marye's Heights in the
Battle of Fredericksburg. Kelly was acting commander of the Irish Brigade at the end of 1862. After the 1863
Battle of Chancellorsville, Kelly was promoted to command the Irish Brigade following the resignation of
Brig. Gen. Thomas Francis Meagher. Kelly led the heavily depleted brigade (fewer than 600 men) in an attack at the
Wheatfield at
Gettysburg. The brigade lost 198 of 532 troops engaged, around 37%. Kelly resumed his role as colonel of his regiment as more senior officers returned to the brigade. However, with the death of Col.
Richard Byrnes at the
Battle of Cold Harbor in 1864, Kelly again commanded the brigade. At the age of 42, Kelly died during the
Siege of Petersburg when he was shot through the head while leading the Irish Brigade forward against Confederate earthworks. His body was recovered and sent back to New York for his funeral. He was buried in
First Calvary Cemetery in
Woodside, New York. ==References==