When the Civil War broke out in 1861, Baird was promoted to
brevet captain. He fought at the
First Battle of Bull Run under
Brig. Gen. Daniel Tyler. On November 12, 1861, Baird was promoted to
major in the
Regular Army while serving as an assistant inspector general. He became chief of staff to
Maj. Gen. Erasmus D. Keyes during the first part of the
Siege of Yorktown, where his service earned him a further promotion to brigadier general of
U.S. Volunteers on April 30, 1862, to rank from April 28, 1862. In April 1862, Baird took command of the 27th Brigade, 7th Division in the
Army of the Ohio under Maj. Gen.
Don Carlos Buell. Baird helped
secure the Cumberland Gap in June 1862 under
George W. Morgan. He commanded the 3rd Division,
Army of Kentucky where his troops fared poorly in the
Battle of Thompson's Station in March 1863, though Baird was not personally involved. His troops were present at the
First Battle of Franklin (Harpeth River) in April, before being assimilated into the
Army of the Cumberland. Baird's division became the 1st Division of Maj. Gen.
George Henry Thomas's
XIV Corps. It was in this post that he won fame for his heroic efforts at the
Battle of Chickamauga and the
Chattanooga campaign. Baird won a brevet promotion to
colonel in Regular Army for Chattanooga. In the
Atlanta campaign, Baird led a brigade charge in the
Battle of Jonesborough which earned him the
Medal of Honor. He led his division in Maj. Gen.
William T. Sherman's
March to the Sea and
Carolinas campaign. Baird led his division in the
Battle of Bentonville in the latter campaign. On January 23, 1865,
President Abraham Lincoln nominated Baird for appointment to the brevet grade of major general of volunteers, to rank from September 1, 1864, and the
U.S. Congress confirmed the award on February 14, 1865. On April 10, 1866, President
Andrew Johnson nominated Baird for appointment as brevet brigadier general in the
Regular Army, to rank from March 13, 1865, and the U.S. Senate confirmed the appointment on May 4, 1866. On July 17, 1866, President Andrew Johnson nominated Baird for appointment as brevet major general in the regular U.S. Army, to rank from March 13, 1865, and the U.S. Senate confirmed the appointment on July 23, 1866. Baird was mustered out of the volunteer service on September 1, 1866. ==Postbellum life==