The Siege of Port Hudson was part of a concerted Union effort to gain full control of the Mississippi River. It was conducted May 22 – July 9, 1863 by forces under the command of Major General Nathaniel Prentice Banks, and only ended because the Confederate General Franklin Gardner surrendered after learning of the fall of Vicksburg, Mississippi to Union forces. General Banks gave orders to two units composed entirely of African Americans, the 1st and 3rd Louisiana Native Guards, to attack the Confederate positions south of Foster Creek on the morning of May 27. There was in Union military circles some question about how these units would perform, which were among the first to include African-American field commanders. The units acquitted themselves well, reaching to within of the Confederate batteries three times before being repulsed. The overall attack plan ordered by Banks was a failure, in part due to the piecemeal, disorganized, and uncoordinated execution of its elements. The units that fought against this position suffered 37 killed, 155 wounded, and 116 missing (out of just over 1,000 men deployed), and remained in the field until ordered to retreat at 4:00 PM.