20th Massachusetts

On August 8, 1861, Bartlett was commissioned captain in a new regiment then forming—the 20th Massachusetts Infantry—and given command of Company I.^[1] It was known as the "Harvard Regiment" because many of its young officers, including Bartlett, were Harvard students or recent graduates. Shortly after arriving in Virginia in September 1861, Capt. Bartlett led his company into battle for the first time when the 20th Massachusetts took part in the Battle of Ball's Bluff on October 21, 1861. The engagement was a great defeat for the Union Army.^[2]

Hoping to avoid any further such defeats, Major General George B. McClellan, the commander of the Army of the Potomac, to which the 20th Massachusetts was attached, developed a plan to by-pass the difficult overland route to the Confederate capital of Richmond. The Peninsular Campaign was intended to be a rapid movement of the Army of the Potomac by water, then by land, up the relatively short Virginia Peninsula. The 20th Massachusetts and Capt. Bartlett were part of this massive movement in the spring of 1862. The campaign stalled, however, when McClellan chose to lay siege to Yorktown, Virginia rather than assaulting the far smaller Confederate force there.^[5] During the siege, on April 24, 1862, Capt. Bartlett was shot in the left knee by Confederate pickets. The wound required the amputation of his leg. Bartlett returned to Boston to recuperate and, during the summer of 1862, finished his degree at Harvard.^[2]

William Francis Bartlett

49th Massachusetts

After completing his degree, Bartlett chose not to re-join the 20th Massachusetts and resigned his commission on November 12, 1862.^[1] Instead, Bartlett accepted a colonel's commission and was placed in charge of forming a new regiment in Berkshire County, Massachusetts—the 49th Massachusetts Infantry. The regiment was to serve a term of nine months.

The 49th Massachusetts was assigned in late November 1862 to the Louisiana expedition of Maj. Gen. Nathaniel P. Banks. The aim of the expedition was to increase the number of Union soldiers in the Army Department of the Gulf and to conquer the few remaining Confederate strongholds on the Mississippi River, thus opening that waterway to the Union. Bartlett led his regiment during the Siege of Port Hudson in Louisiana in the spring of 1863. Due to the amputation of his leg, he was required to remain on horseback during battle, making him an easy target for Confederates.^[4] During one of several assaults on Port Hudson on May 27, 1863, Bartlett was shot twice— a bullet shattered his left wrist, while buckshot struck his right leg. The regimental surgeon, Dr. Frederick Winsor, was able to remove the bullet and save his hand, but the wounds effectively removed him from command until the end of the 49th's term of service in September 1863.^[4] Bartlett resigned his commission on September 1, 1863.^[1]

57th Massachusetts

While still recuperating from his wounds received in Louisiana, Bartlett began to organize, in the fall of 1863, another regiment. This unit, the 57th Massachusetts Infantry was one of four "Veteran Regiments," organized in Massachusetts to consist almost exclusively of men who had already served out an enlistment with a previous regiment.^[6] Bartlett was placed in command of the 57th which was formed in Worcester, Massachusetts. The unit was sent to Virginia before it was fully organized, and Bartlett would not receive his new commission as colonel of the 57th until April 9, 1864, although the commission was made retroactive to August 1863.^[1][4]

The 57th Massachusetts became part of the IX Corps of the Army of the Potomac and arrived at the front in time for Ulysses S. Grant's Overland Campaign; a relentless series of attacks by Union forces during the spring of 1864 aimed at grinding down Robert E. Lee's Army of Northern Virginia. Early in the campaign, Bartlett was again wounded, this time in the head, during the Battle of the Wilderness on May 6, 1864.^[2] He returned to Massachusetts and, while recovering, received a promotion to brigadier general, U.S. Volunteers, on June 22, 1864, to rank from June 20, 1864.^[7] Bartlett returned to the Army of the Potomac in July 1864.

Brigade command

Upon his return, Bartlett was placed in command of a brigade (1st brigade, 1st division of the IX Corps) consisting almost entirely of Massachusetts regiments.^[4] During July, he played a small role in the planning of the Battle of the Crater. This was a bold attempt to break the Siege of Petersburg by digging a mine beneath Confederate entrenchments and detonating a massive amount of gunpowder to create a gap through which Union forces could assault the city. The detonation on July 30, 1864, was successful, but the Union assault was disorganized and failed. Brig. Gen. James H. Ledlie's division, of which Bartlett's brigade was a large part, led the attack. In the battle, Bartlett's prosthetic leg was shot away. Unable to retreat with the rest of his men, Bartlett was captured by Confederates.^[2]

Bartlett spent two months in Libby Prison where he grew severely ill. He was eventually released through a prisoner exchange at the end of September 1864, however it was several months before he recovered from his illness.^[4]

Division command

In June 1865, Bartlett returned to the army two months after the Confederate surrender. Although hostilities had ended, a large portion of the Union Army still remained on active duty and Bartlett was promoted to the command of the 1st Division of the IX Corps on June 17, 1865. On January 13, 1866, President Andrew Johnson nominated Bartlett for the award of the honorary grade of brevet major general, U.S. Volunteers, to rank from March 13, 1865, and on March 12, 1866, the U.S. Senate confirmed the award.^[8] In July 1865, the IX Corps was disbanded, however Bartlett remained in the army another year until his resignation on July 18, 1866.^[1]