The ability of the Union Army to gain and then maintain control of the rivers in Western Theater directly impacted their eventual victory over Confederate forces. In terms of square miles, the Western Theater was almost four times larger than the Eastern Theater so by controlling river travel, large armies were able to cover a lot of ground quickly and it was also vital to getting supplies to the troops.

The Union Army strategically made its’ move to take control of the Mississippi River by moving south with battles at New Madrid, Missouri and Memphis while at the same time they were moving north by taking control of the river from New Orleans through Jackson, Mississippi but all along their real focus was Vicksburg. 

The fight to control the rivers really began on February 6, 1862 when General Ulysses S. Grant and Andrew Foote, the Commander of the Western Gunboat Flotilla, successfully attacked Fort Henry which was located on the Tennessee River, causing Confederate General Lloyd Tilghman to surrender. Then on February 11th, Grant began a five day attack on Fort Donelson, located on the Cumberland River resulting in Fort Donelson’s surrender by Brigadier General Simon Buckner. This gave Union forces control of Kentucky and western Tennessee.

New Orleans’ location at the mouth of the Mississippi River made it an early Union target during the Civil War. New Orleans' major defenses came from Fort Jackson and Fort St.

Phillip that were situated downstream from New Orleans on opposite sides of the river at a spot where there was a bend. The Union began its assault on these forts on April 18, 1862. By the end of April, the Union had control of both of these Forts and New Orleans. New Orleans was captured without a battle in the city, thus preserving its infrastructure and rich history. Union control over New Orleans was a huge blow to the Confederacy due to its’ major role for the South’s cotton exports.

On the Northern end of the Mississippi River, the Battle of Memphis had actually been decided by the Union’s victory at Corinth, Mississippi. The City of Corinth was a key transportation hub, located at juncture of the Mobile and Ohio Railroad and the Memphis and Charleston Railroad. When the Union forces captured Corinth at the end of May 1862, rail travel from Memphis eastward was cut off and therefore Confederate forces deserted Memphis and their nearby forts. On June 6, 1862, after a two hour naval battle Union forces occupied Memphis.

The City of Vicksburg was an important port due its location at the confluence of the Mississippi and Yazoo Rivers. The city was situated atop a high bluff overlooking the Mississippi River which also made this city fortress-like and impregnable against assault by General Grant and his troops. The Siege of Vicksburg began on May 18, 1863 with Grant’s Army of the Tennessee pushing the Confederate Army of Vicksburg led by Lt. General John C. Pemberton towards the City of Vicksburg.  Pemberton had no choice but retreat into Vicksburg because he knew that Major General William T. Sherman was in position to flank Pemberton’s forces from the North.

Grant attacked Vicksburg on May 19th and May 22nd only to sustain a tremendous number of casualties, so Grant reversed course and decided to besiege the city – a strategic move that caused Pemberton to formally surrender his Army of approximately 30,000 troops and the City of Vicksburg on July 4, 1863.

Upon the surrender of Vicksburg, the Union effectively controlled the Mississippi River from north of Memphis to the Gulf of Mexico. By controlling the river, it also meant that the Union forces had also split the Confederacy in half meaning that a large portion of the Confederacy west of the Mississippi could not participate in the war effort.