advisers wanted to save Vicksburg, but Lee persuaded Davis to overrule them and authorize yet another invasion of the North. The immediate goal was to acquire urgently needed supplies from the rich farming districts of Pennsylvania; a long-term goal was to stimulate peace activity in the North by demonstrating the power of the South to invade. Lee's decision proved a significant strategic blunder and cost the Confederacy control of its western regions, and nearly cost Lee his own army as Union forces cut him off from the South. Lee launched the Gettysburg Campaign when he abandoned his position on the Rapahannock and crossed the Potomac River into Maryland in June. Hooker mobilized his men and pursued, but was replaced by Gen. George G. Meade on June 28, a few days before the two armies clashed at the town of Gettysburg, Pennsylvania in early July; the battle produced the largest number of casualties in the American Civil War. Some of Lee's subordinates were new and inexperienced to their commands, and J.E.B. Stuart’s cavalry failed to perform effective reconnaissance. The first day was a surprise affair for both sides, and the Confederates managed to rally their forces first, pushing the panicked Union troops away from town, and towards key terrain that should have been taken by General Ewell, but was not. The second day unfolded differently for the Confederates. They took too much time to assemble, and launched repeated failed assaults against the Union left flank over difficult terrain. Lee's decision on the third day, going against the advice of his best corps commander, Gen. James Longstreet, to launch a massive frontal assault on the center of the Union line, was disastrous. It was carried out over a wide field, and has come to be known commonly as Pickett's Charge. Easily repulsed, Pickett’s Charge, named after the general whose division participated, resulted in severe Confederate losses. Lee rode out to meet the remains of the division and proclaimed, "All this has been my fault." He had no choice but to withdraw, and he escaped Meade's ineffective pursuit, slipping back into Virginia. Following his defeat at Gettysburg, Lee sent a letter of resignation to President Davis on August 8, 1863, but Davis refused Lee's pleads to retire. That fall, Lee and Meade met again in two minor campaigns, Bristoe and Mine Run, that did little to change the strategic standoff. The Confederate Army