Civil War: The First Great Union Offensive in the Western Theater


By Gary Gallagher, Ph.D., University of Virginia

The American Civil War—fought between the Federals, or Unions, who represented the North, and the Confederates, who formed the Southern Army—witnessed a number of attacks from either side, some more influential than others. One of the most important parts of the war was the Union’s offensive in the Western Theater, which went on to decide the outcome of the war.

Map depicting the areas of control in the Western Theater of the American Civil War
The Confederates had to defend a large area in the West, from the Appalachians to the Mississippi River.
(Image: Map by Hal Jespersen, / CC BY 3.0 / Public domain)

There were a number of reasons for which the Western Theater was seen by soldiers and professionals as an area of tantamount importance, which would be integral in deciding the outcome of the war. It was a great area between the Appalachian Mountains and the Mississippi River, where both sides had different, but significant vantage points. While the south had a significant amount of territory there, the Union had been able to establish excellent advances. There, the Confederates had an expansive network of railroads and internal lines that allowed them to progress and fall back as required. Meanwhile, the North had been able to mobilize large numbers with their troops in the West. Further, the Confederates in the West were led by Albert Sidney Johnston, who, being the ‘highest’ de facto ranking officer in the field, was able to lead their troops in the West under a unified overall command.

Of course, such an important battle had to be fought under able leadership, and both parties put their best men to the task. 

The Leaders in the West

The importance of the battle in the Western Theater was reiterated by both parties when they put their most decorated, most essential men to the task. One of the men who led the North to its victory was the General-in-Chief, Winfield Scott. He was pivotal in a lot of strategic planning for the North, though he left the force in November 1861, after being plagued by some health problems, as well as by the defiant attitude of Major General George B. McClennan, who, interestingly, took up Scott’s command after he the latter retired. 

Two men led commands for the Union under Scott: Henry Wager Halleck, and Don Carlos Buell. 

The Union’s primary goals at the time were to identify major advance lines Southward through the west, pacify territories to their side, and take down the opposition’s strategic networks. There was also the political target to liberate Unionists, primarily those in East Tennessee. 

On the other hand, the Confederates in the West were led by the remarkable Albert Sidney Johnston, who was, at the time, touted to be the best soldier in the Confederates’ arsenal. The enormity of the expanse of territory covered by the Confederates, which in some ways also was their strength, now became a strategic nightmare, as they now needed to defend all that is, stretching from the Appalachians to the Mississippi River.

Learn more about the Generals of the Confederacy.

The Confederate Defense Structure in the West

The western frontier under Johnston’s command was vulnerable along four primary routes: the Mississippi River, the Tennessee River, the Cumberland River, and the Louisville and Nashville Railroad; any of these could have proven viable for the Federals. In order to defend all four routes, Johnston deployed his troops along a great arc.

In a bid to protect the heart of Tennessee, the left flank was anchored at Columbus, Kentucky, a very strong, heavily fortified position. On a high strong point on the Mississippi river here, twelve thousand men were deployed. The troops at Columbus were commanded over by Episcopal Bishop Leonidas Polk, who, according to his own troops, was not a man of great military acumen. 

Bowling Green, a small town in Kentucky, which anchored the flank for the confederacy's defense.
Bowling Green, a small town in Kentucky, was imperative during the battle, as it served as an anchor for Johnston’s defensive flank. (Image: Jacob Boomsma/Shutterstock)

On the other hand, the right flank for Johnston’s formation was anchored on the Louis and Nashville Railroad at Bowling Green, Kentucky, where about 25,000 men were present. 

Within the arch, there were a pair of forts intended to guard the Cumberland and Tennessee Rivers: Fort Henry on the Tennessee, and Fort Donelson on the Cumberland. However, Johnston didn’t give too much of his attention to either, focusing instead on his flanks. Two final components of the Confederate forces in the west were a small army in Arkansas led by General Earl Van Dorn, and another small one, led by Officer Felix Zollicoffer, near the Cumberland gap.

Learn more about the Slaveholding States.

The Great Union Offense

The offensive position taken by the Union in the Western Theater went on to become a pivotal point, as it would turn out to be the first successful major Union military operation during the war. 

For their offense, both the leading commanders of Scott’s Union forces, Halleck and Buell, agreed that the weakest points in Johnston’s defense were through Fort Donelson on the Cumberland and Fort Henry on the Tennessee River. Incidentally, both the points fell in Halleck’s department, so it was he who formulated plans to not only take down these forts but also to cut the railroad that ran from Memphis to Bowling Green, thereby denying the Confederacy their precious interior lines.

Nashville, then a rail, manufacturing center, and supply center, was also noted as one of the key targets, as one of the most important cities in Tennessee at the time.

This is a transcript from the video series The American Civil War. Watch it now, on The Great Courses Plus.

Early Union Victories

Felix Zollicoffer, a general in Johnston's army, who was martyred in Mill Springs.
General Felix Zollicoffer became one of the Confederate’s early war heroes when he was martyred at the Battle of Mill Springs. (Unattributed/Public domain)

Before Halleck put his overall plan in motion, there were a few smaller-scale plans put to action. An important one of these was conducted by George H. Thomas, one of Buell’s important men, who, in January 1862, took down Felix Zollicoffer’s small Southern force at the Battle of Mill Springs, on the Cumberland River. 

While this defeat marked the first crack in Albert Sidney Johnston’s western line by forcing the confederates to back away from eastern Kentucky, it also gave them an early war hero, as Zollicoffer was martyred in the battle.

Battles at Fort Henry and Fort Donelson

After a series of minor early victories, the Union set out to set Halleck’s plan in motion, for which the significant fighting would come at Fort Henry and Fort Donelson. Ulysses S. Grant was selected to lead the forces ahead.  Halleck needed to clean up Missouri to make it safer for the Union, after which he was to move into Confederacy territory along either of the three rivers. In Missouri, he gave Grant a force of about 15,000 men and instructed him to move up the Tennessee River towards Fort Henry.

Grant used Tennessee as his route, reaching Fort Henry first, which fell easily, as it was a weak establishment. He then proceeded to cut the railroad and focus his attention on Fort Donelson. 

Although Donelson boasted of much more robust construction in comparison to Henry, it was still a vulnerable target, and Grant’s approach, combined with a series of serious mistakes on Johnston’s part meant that soon enough, Fort Donelson fell as well. 

Fall of the Confederate forces

The fall of Fort Donelson was a momentous occasion: it led to the Fall of the Confederate forces in Nashville and subsequently culminated into the Confederate forces abandoning their entire line in the Western Theater. Their defeat forced them to retreat, and the Union gained control over several important parts of the West. 

Johnston hailed as a super – soldier, had not lived up to the many expectations placed on him. He was criticized for his strategic miscalculations, as well as for under-utilizing the Confederacy’s internal lines, and for not concentrating his troops well enough.

He ended up losing 25 percent of his troops, and his entire defense. This battle, waged in the wee months of 1862, had brought great news for the Union, but the war was still ongoing, and both parties continued to fight on. 

Commonly Asked Questions about The Great Offense on the Western Theater

Q: How did Albert Sidney Johnston plan to protect Confederate territory in the Western Theater?

Albert Sidney Johnston planned to deploy his troops along a great arc along with the Western Theater, with flanks at Columbus, Kentucky, and Bowling Green, Kentucky.

Q: What was the offense planned by Henry Wager Halleck?

Henry Wager Halleck planned to attack Confederate territory on the Western Frontier by taking down Fort Henry and Fort Donelson and cutting the Memphis and Ohio Railroad.

Q: What role did Ulysses S. Grant play in the offense on the Western Theater?

Ulysses S. Grant was recruited by Henry Wager Halleck to carry out his offensive strategy on the confederate territory in the Western Theater.

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