Greer was promoted to lieutenant commander and served on the from 1862 to 1863, and then was attached to Rear Admiral David Dixon Porter's Mississippi Squadron.<unk> Greer was promoted to lieutenant commander and served on the from 1862 to 1863, and then was attached to Rear Admiral David Dixon Porter's Mississippi Squadron. While in command of the ironclads and, he participated in the Vicksburg campaign and the shelling of
Grand Gulf as well as the abortive Union Red River expedition in early 1864.