<P> 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 more than 12,000 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 . </P> <P> 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 . Gen. Stonewall Jackson was shot in the arm by accidental friendly fire during the battle and subsequently died of complications . Gen. Hooker 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 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 . </P> <P> While the Confederate forces had numerous successes in the Eastern Theater, they were defeated many times in the West . They were driven from Missouri early in the war as a result of the Battle of Pea Ridge . Leonidas Polk's invasion of Columbus, Kentucky ended Kentucky's policy of neutrality and turned that state against the Confederacy . Nashville and central Tennessee fell to the Union early in 1862, leading to attrition of local food supplies and livestock and a breakdown in social organization . </P> <P> The Mississippi was opened to Union traffic to the southern border of Tennessee with the taking of Island No. 10 and New Madrid, Missouri, and then Memphis, Tennessee . In April 1862, the Union Navy captured New Orleans, which allowed Union forces to begin moving up the Mississippi . Only the fortress city of Vicksburg, Mississippi, prevented Union control of the entire river . </P>

What was one major outcome of the north winning the u.s. civil war