Nathaniel Banks, commander of the Union Department of the Gulf, surrounds the Confederate stronghold at Port Hudson, Louisiana, and attacks. Fortifications were built at Port Hudson in 1863 to protect New Orleans from a Union attack down the Mississippi River. On April 25, 1862, New Orleans had fallen into Union hands following an attack from the Gulf of Mexico by Admiral David Farragut. Still, Port Hudson was considered an important installation for the South since it was a significant threat to Federal ships on the Mississippi River.
In 1863, the Union command began to focus attention on clearing the Mississippi of all Rebels. The major thrust of this effort was taking Vicksburg, Mississippi, the Confederate stronghold to the north of Port Hudson. In April, Ulysses S. Grant summoned Nathaniel Banks to participate in the campaign against Vicksburg.
Banks wavered at first, preferring instead to wage an independent campaign against Confederates in Louisiana. But in May, he set out to take Port Hudson, then under the command of Franklin Gardner. Banks had some 30,000 troops under his command, while Gardner possessed a force of just 3,500. When Banks began to encircle Port Hudson, Gardner made some feeble attacks to drive him away.
On May 21, Gardner received orders from Joseph Johnston, operating in Mississippi, to abandon the fort. But Gardner refused, and asked for reinforcements. This was a fatal mistake, and Banks soon had Gardner surrounded. For the next three weeks, Banks attempted to capture Port Hudson but failed each time. It was not until Vicksburg surrendered on July 4 that Gardner also surrendered.