The following year, he participated in the Vicksburg Campaign, conducting a raid in Mississippi. Crocker had brought his brigade to a high state of discipline, and it was nicknamed "Crocker's Greyhounds" for its swift marching ability. After the re-enlistment of his brigade as veteran volunteers, he assumed command of a division when General Isaac F. Quinby went on sick leave. Crocker led his division into action at the Battle of Jackson. On the morning of May 16, General Quinby returned to duty. However it was deemed necessary to retain Crocker in command of the division as it was deploying for battle at Champion Hill. Crocker received praise for his actions in that battle.