History of the 121st Pennsylvania Volunteers
The 121st regiment joined the 5th Corps on June 6, 1864. It was placed in the First Brigade of the First Division that was newly formed.
Chamberlain having lost command of the third Brigade to General Bartlett, a ranking officer who recently joined the Division, was given this new command that was equally impressive.
Having served under Chamberlain for a little over ten days it is no wonder that this regiment did not know him too well, here they erroneously state, "Colonel J. L. Chamberlain of the first Maine Infantry." It does not appear from this narrative that they had much contact with Chamberlain when this was written in 1893.
To read the "History of the Pennsylvania Volunteers" very brief description of Petersburg follow the below link:
121st in "History of the Pennsylvania Volunteers"