By the summer of 1862, the Union had won a string of major victories in the West. But the war was about to swing violently back east. At Second Manassas in late August 1862, Robert E. Lee and Stonewall Jackson executed one of the most decisive campaigns of the entire Civil War, routing a Union army of 70,000 men and setting the stage for the first Confederate invasion of the North.

Key Takeaways

• By June 1862, Union forces had captured 50,000 square miles of Confederate territory, two Confederate capital cities, and the South's largest city, New Orleans.

• General George McClellan repeatedly overestimated Confederate troop strength, at one point claiming Lee had 200,000 men when the actual number was closer to 90,000.

• Stonewall Jackson's corps marched over 50 miles in two days to strike Pope's supply line at Manassas Junction, a maneuver that drew the Union into a trap.

• McClellan's failure to send reinforcements to Pope during the Second Manassas battle contributed directly to the Union defeat.

• After Second Manassas, Lee immediately launched the Maryland Campaign, which would culminate in the bloodiest single day in American military history at Antietam.

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Questions & Answers (FAQ)

Q1: Why did Lee attack rather than defend Richmond in June 1862?

Lee concluded that Richmond could not withstand a prolonged siege by McClellan's large army. His only viable option was to attack aggressively, disrupt McClellan's plans, and drive Union forces away from the Confederate capital. The Seven Days Battles achieved that goal, though at a very high cost in Confederate casualties.

Q2: What was Stonewall Jackson's role at Second Manassas?

Jackson led roughly 25,000 Confederate troops on a rapid flanking march around Pope's army, covering more than 50 miles in two days to strike the Union supply base at Manassas Junction. He then took up a defensive position along an unfinished railroad embankment and held it against repeated Union attacks, drawing Pope into repeated costly assaults while Longstreet's corps arrived to deliver the decisive blow.

Q3: Why didn't McClellan reinforce Pope during Second Manassas?

McClellan and Pope had a poor relationship, and McClellan was deeply reluctant to operate under anyone else's authority. He kept his forces near Washington in a defensive posture rather than moving to support Pope's army. His inaction contributed directly to the Union defeat, and it deepened Lincoln's doubts about his willingness to fight aggressively.

Q4: How many casualties did each side suffer at Second Manassas?

Union forces suffered approximately 14,000 casualties killed, wounded, or captured. Confederate losses were around 8,000. Despite the lower Confederate casualty count, the battle's strategic impact was decisive, routing a 70,000-man Union army and opening the door for Lee's first invasion of northern territory in the Maryland Campaign.

Q5: What came immediately after the Confederate victory at Second Manassas?

Lee moved directly from Second Manassas into the Maryland Campaign, crossing the Potomac River and invading the North for the first time. This led to the Battle of Antietam on September 17th, 1862, which became the single bloodiest day in American military history, with over 22,000 casualties in a single day of fighting.

A Great Wave of Union Victories in the West

From February through May of 1862, there was a great wave of Union victories in the Western Theater. By June that year, the Union had taken control of 50,000 square miles of Confederate territory, over 1,000 miles of important riverways, and captured two capital cities, Nashville and Baton Rouge, plus the largest city in the South, New Orleans. Northern forces had killed, wounded, or imprisoned over 30,000 rebel troops. But now the war swung back east, and the Union wave would end in Virginia. A year earlier, both armies had clashed on this same Virginia ground, as we cover in our episode on the First Battle of Bull Run.

McClellan and the Peninsula Campaign

On April 2nd, 1862, Union General George B. McClellan and his army landed at Fort Monroe, Virginia. He then advanced up the Virginia Peninsula with an army of nearly 100,000 men, besieging Yorktown, then confronting forces led by James Longstreet and Joseph E. Johnston in the Battle of Williamsburg. Marked by heavy rains, the battle ended inconclusively. McClellan marched on, casting a general doom over the South as he came within six miles of Richmond, the Confederate capital.

On May 31st, 1862, General Johnston, the leading Confederate general at the time, was severely wounded in the Battle of Seven Pines. Shortly afterward, Confederate President Jefferson Davis gave Virginian Robert E. Lee command of the Confederate army. Lee did not believe that the Southern forces could hold Richmond against a Union attack, but he would neither surrender nor retreat. The only option was to attack. Lee had roughly 90,000 troops in his command, including 25,000 to 30,000 led by Stonewall Jackson. McClellan grossly miscalculated that he was outnumbered by the Confederates. The Western theater had recently exploded in violence, as we cover in our episode on the Battle of Shiloh.

The Seven Days Battles

On June 25th, McClellan telegraphed Secretary of War Edwin Stanton: "The rebel force is stated at 200,000, including Jackson. I shall have to contend with vastly superior odds." Beginning the next day, Lee launched a series of coordinated attacks known as the Seven Days Battles. On June 27th, one day after Lee began his assaults, McClellan chose to retreat toward the James River rather than press forward.

The battles at Mechanicsville and Gaines' Mill saw fierce fighting, with Lee willing to take heavy losses in order to push McClellan back. Over the next several days at Savage's Station, Glendale, and Malvern Hill, Union forces frequently held defensive advantages, inflicting severe casualties on the attacking Confederates. By the end of the seven days, the Union had suffered around 16,000 casualties, while Confederate losses approached 20,000. It was the bloodiest week up to that point in all of American history. Despite these higher losses, Lee had saved Richmond. In the North, frustration with McClellan's cautious leadership grew, and confidence in a quick victory in the war declined.

Pope's Defeat and Lee Invades the North

Union leadership reorganized its forces in Virginia, creating a new army under General John Pope numbering about 70,000 men. Lee sent Stonewall Jackson with about 25,000 men to strike Pope's flank and disrupt his supply lines. Jackson captured key positions near Manassas, drawing Union forces into battle along an unfinished railroad line. The raised embankments there gave the rebels cover and protection. Believing Jackson was isolated, Pope launched repeated attacks against his entrenched position. Unbeknownst to Pope, however, General James Longstreet had arrived with another 30,000 Confederate troops. On August 30th, 1862, Longstreet launched a massive flank attack that crushed the Union left and sent Pope's army into retreat. The Second Battle of Manassas ended in a decisive Confederate victory.

Union forces suffered approximately 14,000 casualties while Confederate losses were around 8,000. Following the triumph at Second Manassas, Lee chose to invade the North, launching the Maryland Campaign. The country was in for a whole new level of carnage when Lee and McClellan would meet at Antietam, less than three weeks after the Confederates defeated Union forces at Manassas for a second time. The Union victory in the West that bookended this Eastern reversal is the subject of our episode on the Union capture of New Orleans.