When the US Civil War began Rosencrans volunteered to be an aid to General George B. McClellan. In summary form here are the events that brought Rosencrans to become a key to Union military operations in Tennessee:1. He became a brigadier general and participated in General McClellan's operations in western Virginia;
2. When McClellan left to take command of the Army of the Potomac, Rosencrans served as commander of the departments of Ohio and Western Virginia;
3. Rosencrans left Virginia to command a division in the Army of the Mississippi;
4. He was promoted to be the commander of the Army of the Mississippi;
5. This placed him under the direct command of US Grant;
6. Rosencrans fought his first major battle at Iuka Mississippi and won the battle;
7. US Grant was disturbed at Rosencrans because he failed to follow Grant's orders to pursue the enemy;
8. At this juncture, ill feelings between the generals began;
9. At the Battle of Corinth in 1862, Rosencrans again was the victor, however, he failed to pursue the enemy; and
10. Rosencrans was reassigned to the Army of the Cumberland, and thus fought Confederate General Braxton Bragg in Tennessee.
General Rosencrans was successful in preparing his Army of the Cumberland in 1863. He then began his offensive against Confederate General Braxton Bragg in June of 1863.
General Meade, still in command of the Army of the Potomac was forced to send two corps to Tennessee to help reinforce General Rosencrans.
Based on Union General Rosencrans' retreat to Chattanooga after the Battle of Chickamauga, Confederate General Bragg could take a position on the south side of the Tennessee River. In this position Bragg could force a greater retreat by the Union army because Bragg could cut the rail link Rosencrans needed to bring in supplies.
Union General Rosencrans had a brilliant plan to drive Confederate Braxton Bragg and the Army of Tennessee out of Middle Tennessee. It was a two step plan which began by deceiving Bragg concerning the location of the Union's location for its main attack. Bragg had dug in behind entrenchments and to draw him away, Rosencrans would move a sizable number of troops in a false direction. Bragg could not afford not to follow.The second part of the plan was to move Rosencrans' main force in an envelope maneuver and attack Bragg's rear side and cut off Confederate communication lines. Bragg would be forced to retreat in a disadvantaged position to protect his lines or choose to fight where he would be in a poor position to do so. With any luck, Bragg would chose to retreat rather than lose his lines of communications. With any luck, Bragg would be forced out of Middle Tennessee without any shots even being fired. This was Rosencrans' main objective.
Major General William Starke Rosencrans for the Union Army of the Cumberland and Lt. General Braxton Bragg for the Confederate Army of Tennessee.
There were few, if any, major military actions in 1863 that did not have the approval of US President Lincoln or his Secretary of War, Edwin Stanton. With that said, the answer was yes regarding pressure from Washington DC placed on General Rosencrans. On July 7, 1863, he received a strongly worded message from Secretary Stanton to advance onward to Chattanooga, Tennessee. Rosencrans was informed that he needed to do his part to seal the fate of the Confederacy. Rosencrans was informed that Lee's army in Pennsylvania was in retreat and that Grant had things well under control regarding Vicksburg. Stanton "ordered" Rosencrans to march on Chattanooga.
Union General US Grant was basically placed in charge of the Western Theater of the US Civil War. He, as did Lincoln, lost all faith in General Rosencrans. He therefore replaced Rosencrans with General George H. Thomas.
Based on his tactics against Confederate General Bragg in Tennessee, General Rosencrans had without even engaging the enemy, advanced his army in little more than a week, four times as fast as he had after his victory at Murfreesboro.Union Secretary of War Edwin Stanton was not impressed with the news from Rosencrans. Stanton was still upset over the delays that Rosencrans created by being overly cautious. Stanton's attitude concerning this delay was easy to express, however, Stanton had never commanded an army.Halleck, as general in chief, was the person to admonish Rosencrans, not Stanton or even President Lincoln.
US President Lincoln pressured Union General Rosencrans to move against the Army of Tennessee, commanded by Braxton Bragg in June of 1863. Rosencrans was successful in forcing Bragg to retreat to Chattanooga on July 7, 1863. After Union victories at Gettysburg and Vicksburg, President Lincoln sought to take control of southeastern Tennessee. The strategy was to defeat Bragg abd take control of Chattanooga, Tennessee and thereby facilitate a course set on the South's last major rail center in Atlanta. To Lincoln's dismay, Rosencrans did not press an attack on Chattanooga. Finally, after more pressure from Lincoln, Rosencrans took a better course. He swung around Chattanooga into Northwest Georgia threatening Bragg's supply and communications lines. This forced Bragg to evacuate the city allowing Rosencrans to take the city with only a small force.
In late October of 1862, Major General William Rosencrans took over the Army of the Cumberland from General Don Carlos Buell. Hallecks instructions to Rosencrans were the following:* Apply pressure on the Confederate Army of Tennessee and force it out of Kentucky; * Cover Nashville and repair the railroad to permit the movement of supples between Nashville and Louisville, Kentucky; and * Maintain pressure on the Army of Tennessee to prevent it from moving West to hinder the operations of General US Grant.
After many delays, Union General Rosencrans finally began to move his army southwards. He distracted Rebel General Braxton Bragg with a feint move to the west. However, with that said, Rosencrans carried all his supplies with him and marched his entire army to Bragg's right side. Bragg could either attack to protect his own now threatened communications lines or as he did, retreat to protect them. Bragg's army then settled in to the south bank of the Tennessee River, near Chattanooga.
When General William Rosencrans was placed in charge of the Army of the Cumberland, he had to face Confederate General Braxton Bragg. At the battle of Stone's River, Rosencrans forced Bragg to retreat. The casualties in that battle were severe for both sides. Twenty four thousand casualties were the result. Rosencrans rallied on the second day of the battle and forced Bragg to retreat.