General Robert E. Lee's Confederate Army of Northern Virginia was at the height of its power during the days leading up to the invasion of Pennsylvania. Lee's army had, only a month before, driven the much larger Union Army of the Potomac out of Virginia during the climactic Battle of Chancellorsville. But Lee's "right hand," Lieutenant General T. J. "Stonewall" Jackson, had been mortally wounded shortly after his devastating surprise attack on the Union's right flank, and Lee now entrusted his two new reorganized corps to the hands of new commanders: Dick Ewell and A. P. Hill. Lee knew that his old "war horse," James Longstreet, could be counted on to wisely handle his own corps, and Lee believed the time was right for another invasion of the North. Lee believed his army was unbeatable, and his men felt likewise. However, Lee would soon find that the faults of his new corps commanders would lead to indecision (especially by Ewell) and, eventually, defeat.
The Army of the Potomac, fresh from yet another drubbing by Lee's army, had a new commander. Gone was the pompous Major General Joe Hooker; at least one other man had turned down the job before Abraham Lincoln decided upon Major General George Meade. A careful, cautious man, Meade was a surprise choice, and the army was still in turmoil when Lee crossed into Maryland and then Pennsylvania. Meade had to rush his forces to the little college town of Gettysburg when it was determined that Lee's army had arrived there in force. The success of Lee's invasion seemed a foregone conclusion, but for once the Army of Potomac decided to stand and fight. Union cavalry, led by Brigadier General John Buford, managed to hold off the first Confederate divisions; and more Federal troops, under the command of Major General Winfield Scott Hancock, arrived on the field. By the end of the first day of the battle, Union forces commanded several key positions outside Gettysburg. Ewell had failed to take a key position, as "suggested" by Lee, and Federal troop implacements were strong.
Heroes would emerge on both sides, something somewhat new for the Army of the Potomac. Meade's strategy was successful; Colonel Joshua Chamberlain won the Congressional Medal of Honor for his remarkable stand on Little Round Top on the second day; and Hancock's corps held off the charge by 15,000 rebels under Major General George Pickett on the third day. As for the Confederates, Lee's army suffered more than 30% casualties, and his army would never be the same again. Several of Lee's subordinates--Ewell, Hill, cavalry commander J. E. B. Stuart and, even to some degree Lonsgtreet--had failed him. Even worse for Lee, Lincoln decided yet another man would lead the Army of the Potomac: Superceding Meade would be the man who had won so many battles in the West--Ulysses S. Grant. In the months to come, Grant would be the one man that Lee could not overcome.