By the start of 1865 the only port still open to the Confederacy was Wilmington, North Carolina. The port itself was located twenty miles up the Cape Fear River. The mouth of the river was protected by Fort Fisher, a massive fortification almost one mile long as it faced the Atlantic. Built of sand over a log framework it was almost impervious to Union bombardment. The fort mounted 47 big guns, and dominated the approaches to the river (twenty guns on the landward side, the rest facing out to sea).
The first Union attack on Fort Fisher had been something of a fiasco. General Benjamin Butler had decided to sink a ship full of gunpowder in front of the fort in the expectation that it would blow a hole in the defences for the Union soldiers. The explosion took place, but failed to have any impact on the defences. Butler managed to land his infantry in front of the still-intact fort, but abandoned any attempt to make an assault in the face of strong undamaged defences.
After this failure, Butler was removed from command and replaced by General Alfred Terry. Terry had the support of a Federal fleet sixty strong, and an army 8,000 strong, as well as a force of marines. Against him the defenders of the fort could muster 2,000 men.
Terry tried a more traditional attack. On 13 January he landed his infantry north of the fort, at the same time as beginning a massive naval bombardment that slowly knocked out all of the landward guns, or made them too dangerous to fire. The bombardment went on for two days, before Terry launched his infantry attack on 15 January. 4,500 infantry attacked along the peninsula, while another 2,000 marines attacked from the Atlantic shore.
Despite the bombardment, the Confederate position was still a strong one, and the outnumbered defenders managed to inflict 1,000 casualties on the attackers (184 dead, 749 wounded and 22 missing) before finally being forced to surrender. The loss of Fort Fisher shut Willington as a blockading port. It helped Sherman in his march through the Carolinas, and Grant in front of Richmond. Lee’s last source of overseas supplies was shut.