In order to fuel, supply, and maintain blockade operations along the southern Atlantic coast the Federal military required a base of operations.  On November 7th, 1861 the Union Army and Navy gained access to Port Royal Sound, capturing the city of Beaufort and Hilton Head Island, South Carolina.  Control of this port gave the Union the base it needed to manage blockades on the southern Atlantic coast.
         On November 10th, the Confederates abandoned Big Tybee Island fearing it was a tactically untenable position and impossible to hold.  Union forces quickly occupied it and established a strong garrison.  Brigadier General Thomas W. Sherman, commander of the Army forces at Beaufort, decided to first isolate the fort from its supply base at Savannah, then pound the fort into submission from batteries constructed on Big Tybee Island.
         The isolation of the fort began in early February 1862.  On February 11th the Union Army completed a gun battery on the mud flats of Jones Island upriver from Fort Pulaski.  This battery ended the majority of river travel between Savannah and the fort.  Although smaller vessels launched from nearby islands could still reach Cockspur Island, Fort Pulaski was alone.