Thank you for this post! It is a great question. At the risk of breaking character I will answer honestly
Banks was appointed as a political general and was a good politician and a decent man but he was not as we know a military man. It is worth considering why he was placed in charge, after the capture of New Orleans by the gallant admiral Farragut. Benjamin Butler was placed in command of the city as a political leader and a military leader of the garrison. Controversy with Butler compelled the president to replace him but a politically able and experienced man would be preferred. Banks was progressive an abolitionist and an early member of the Republican Party and due to his political influence as a popular governor of Massachusetts he was promoted to major general very early to rally his and other states to the cause.His political views can be said to be ahead of the times but this was hardly unique in Massachusetts but made him the man to reconstruct Louisiana as it were.
It is important to note that much of this time he was simultaneously wartime governor of Louisiana (what was not controlled by the rebellion) tasked with implementing Lincoln's plan of reconstruction and a major general tasked with opening the Mississippi from the department of the gulf. He was effective in the former implementing abolition and the recruitment of freedman for the cause while not causing the resentment Butler did. In the latter however he was ineffective and was slow in assistance to Grant and did not capture the relatively smaller port Hudson until after Grant captured Vicksburg.
The Red River campaign has some strategic sense and much political and diplomatic importantance. Going all the way to the top Lincoln was incredibly anxious to raise the flag of our nation on the shores of Texas. The primary reason for the urgency was the ongoing French invasion of Mexico. This intervention was a flagrant violation of the Monroe doctrine and threatened opening a route for supply, diplomatic support and even outright military support to the rebellion by the French. There were also loyal mostly German citizens of Texas not unlike East Tennessee who suffered greatly under occupation by the rebellion. There was a large force under General smith west of the Mississippi that could possibly prolong the conflict if allowed to prosper. A final reason was the supply of cotton in the area. The loss of southern cotton had a large negative impact on north eastern textile mills with a profound negative impact on the employment economy and morale of that section not unlike the impact the previous closure of the Mississippi had on the midwestern state prior to Vicksburg, Banks being from Massachusetts was very aware of these concerns.
The initial plan created by me (Henry Halleck) after it was noted that amphibious assault would yield either failure or at best some meaningless rocks which would not solve any of the above problems. I naively assuming a competent field commander or at least one with capable advisors, created a plan to move upon Shreveport. The plan composed of a thrust down from Little Rock and a push up the red with the navy and army cooperating. I am compelled to note here as I did before Congress that I did not order the campaign but in line with the presidents imperative suggested it to the commanders in the field as a means of accomplishing the end. I never envisioned the Cotton filled greed and disaster that ensued. It was not my fault.
Banks made several errors that proved he was not possessed of the skill required for the undertaking. For reasons entirely unclear to me against all good judgment banks separated his command from the fleet under Porter at Grand Ecore roughly 50 miles from his objective despite good roads running parallel to the river. As Porter would say after his expedition on the yazoo a year prior "I never knew before how much the comfort and safety of ironclads, situated as they were, depended on the soldiers." The fleet could have likewise have protected the army in any battle. Porter and Banks were both blinded by cotton with Porter loading his ships with it and banks even bringing speculators from New England. It is possible these were down with the intention of depriving the enemy of goods and raising the economy and morale of the loyal states. Finally he failed to concentrate his forces and protect his supplies at the battle of Sabine crossroads as any half competent west pointer would have done for gods sake he had his supply in front of much of his army.
The campaign failed in all three fronts but the disaster was not in the casualties or the capture of any section of the force in whole but by the lack of their use in other critical areas of the war. Bank's force originally based at New Orleans was exhausted and demoralized to an extent that an attack upon the vital port city of Mobile Alabama was entirely impracticable. The Navy carried a force under General AJ Smith loaned from Sherman and the army of the Tennessee to protect the navy these troops were needed to protect the fleet from destruction after being trapped by low water on the red and were unable to join his Atlanta campaign as he explicitly said to banks that they must be returned.
I am not in the practice of dictating to field commanders in details of campaigns. The fault of the campaign and its failure belong to banks more than any man,
Very respectfully, your obedient servant,
H. W. Halleck
Bringing the