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.

He commanded the 3rd Division, Army of Kentucky where his troops fared poorly in the battle of Thompson's Station though Baird was not personally involved.

In the Atlanta Campaign, Baird led a brigade charge in the Battle of Jonesborough which earned him the Medal of Honor.

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.

[5] On April 22, 1896, Baird was awarded the Medal of Honor for leading "an assault upon the enemy's works" at the Battle of Jonesborough on September 1, 1864.

[5] He was also a veteran companion of the Military Order of the Loyal Legion of the United States and a member of the General Society of Colonial Wars.