In April 1863, the corps was involved in the actions at Fort Bisland and Irish Bend. It operated the Siege of Port Hudson from April 27–July 9, 1863, the fall of which, along with that of Vicksburg, Mississippi, closed off the Mississippi River to Confederate shipping. XIX Corps also gained measure of distinction for being the first Federal unit to use a large number of colored troops in action, particularly against Port Hudson, with Banks giving them due credit for their valiant contributions to the siege.