Dahlgren asks the army for help
Dahlgren wrote to Gillmore from the flagship off Morris Island that his limited means for operating on the interior lines of the harbor made it very desirable that the enemy’s resistance be reduced as much as possible by whatever means the army possessed. Neither service could take Charleston, and after September 1863 each spent a good deal of ink saying so to the other.
Official Records, Series I, Vol. 28, Pt. 2