Troop engagements of the American Civil War, 1862

During the summer and early spring of the year, Union forces gained several successes over the Confederacy, seizing control of Missouri, northern Arkansas, Kentucky, and western Tennessee, along with several coastal areas.

In the Eastern Theater, the Union Army of the Potomac, commanded by Major General George B. McClellan, was transported to Fort Monroe in April to begin an offensive against Richmond, Virginia.

While the Confederate attacks were often disjointed and several commands failed to arrive at their assigned destinations on time, Lee was still able to drive the Union army back to Harrison's Landing, forcing McClellan to give up his attempt to capture Richmond.

Lincoln replaced McClellan on November 7[7] with Major General Ambrose Burnside, who hoped to cross the Rappahannock River near Fredericksburg, Virginia in order to get between Lee and Richmond.

However, delays in obtaining a pontoon bridge prevented Burnside from crossing the river until December 11, by which time Lee was able to concentrate his entire army along a series of ridges near Fredericksburg.

[9] Johnston, following a plan proposed by his second-in-command General P. G. T. Beauregard, concentrated as many forces as he could near Corinth, Mississippi and attacked Grant's Army of the Tennessee near Shiloh Church.

Fearing that a full scale Union assault on the Confederate defenses was imminent, Beauregard evacuated Corinth during the night of May 29–30 without Halleck's forces finding out until the following morning.

[12] Bragg, pondering how to counteract the Union threat, received a message from Lieutenant General Edmund Kirby Smith, commander of the Confederate Department of East Tennessee, suggesting that the two combine forces to defeat Buell and retake Kentucky.

[15] In April, a Union squadron commanded by Commodore David Farragut ran past Forts Jackson and St. Philip near the mouth of the Mississippi River and forced the surrender of New Orleans, the largest Confederate port city in both population and in trade volume.

Continuing northward along the Rio Grande and the Santa Fe Tail, his brigade met a Union force, which included the 1st Colorado Infantry, at Glorieta Pass on March 28.