History: American Civil War (1861-1865)

Emboldened by Second Bull Run, the Confederacy made its first invasion of the North. General Lee led 45,000 men of the Army of Northern Virginia across the Potomac River into Maryland on September 5. Lincoln then restored Pope's troops to McClellan. McClellan and Lee fought at the Battle of Antietam near Sharpsburg, Maryland, on September 17, 1862, the bloodiest single day in United States military history. Lee's army, checked at last, returned to Virginia before McClellan could destroy it. Antietam is considered a Union victory because it halted Lee's invasion of the North and provided an opportunity for Lincoln to announce his Emancipation Proclamation.
When the cautious McClellan failed to follow up on Antietam, he was replaced by Maj. Gen. Ambrose Burnside. Burnside was soon defeated at the Battle of Fredericksburg on December 13, 1862, when over twelve thousand Union soldiers were killed or wounded during repeated futile frontal assaults against Marye's Heights. After the battle, Burnside was replaced by Maj. Gen. Joseph Hooker. Hooker, too, proved unable to defeat Lee's army; despite outnumbering the Confederates by more than two to one, he was humiliated in the Battle of Chancellorsville in May 1863. He was replaced by Maj. Gen. George Meade during Lee's second invasion of the North, in June. Meade defeated Lee at the Battle of Gettysburg (July 1 to July 3, 1863). This was the bloodiest battle of the war, and has been called the war's turning point. Pickett's Charge on July 3 is often considered the high-water mark of the Confederacy because it signaled the collapse of serious Confederate threats of victory. Lee's army suffered 28,000 casualties (versus Meade's 23,000). However, Lincoln was angry that Meade failed to intercept Lee's retreat, and after Meade's inconclusive fall campaign, Lincoln turned to the Western Theater for new leadership. At the same time the Confederate stronghold of Vicksburg surrendered, giving the Union control of the Mississippi River, permanently isolating the western Confederacy, and producing the new leader Lincoln needed, Ulysses S. Grant.