Colonel Bartlett began recruiting 57th Massachusetts in the summer of 1863. The recruits came from the western part of the state. The rendezvous and camp of instruction was Camp Wool in Worcester, Massachusetts. Bartlett, a veteran of the 4th Battalion Massachusetts Infantry, the 20th Massachusetts Infantry, and the 49th Massachusetts Infantry was already considered a war hero. At age 20, he set aside his studies at Harvard College to enlist as a private. After serving his 90-day term, Bartlett became a captain in the 20th Massachusetts. He was shot in the knee during the Siege of Yorktown--a wound which required the amputation of his leg. In the summer of 1862, he returned to Massachusetts to recuperate, finish his studies at Harvard, and then organized and commanded the 49th Massachusetts. Leading that regiment in the field during the Siege of Port Hudson, Louisiana, Bartlett was again wounded. The wound badly shattered his arm and wrist and effectively removed him from command. After a very short period of recovery, he began recruiting the 57th Massachusetts. He was commissioned as its colonel on August 17, 1863.