Final answer:
Gen. Lee believed a Confederate victory could be achieved by launching a successful invasion into the North, threatening Washington, and gaining decisive territorial advances. However, Union defenses, particularly at the Battle of Gettysburg, prevented this and ultimately led to decisive Union victories.
Step-by-step explanation:
General Robert E. Lee was confident that the Confederate forces could win battles during the Civil War if they managed to strike a significant victory against the Union forces by capturing territory and threatening Washington. Lee invaded Pennsylvania with the hope of bringing a swift end to the war, which he believed could be accelerated by such a decisive action. His counterpart, Union Commander Major General George Gordon Meade, understood the strategic importance of protecting Washington and positioned the Army of the Potomac to thwart Lee's objectives, culminating in the pivotal Battle of Gettysburg. Despite Lee's initiative, the Union forces managed to not only prevent the Confederates from capturing critical locations but also to win significant battles at Gettysburg and Vicksburg, which turned the tide of the war in favor of the Union.