The most famous and most important Civil War Battle occurred on July 1 to July 3, 1863, around the small market town of Gettysburg, Pennsylvania. It began as a small encounter, but, by the time it ended, it involved 160,000 Americans.
Before the Battle, major cities in the North as Philadelphia, Baltimore, and Washington were under.
Threat of the attack from General Robert E. Lee's Confederate Army of Northern Virginia, that had crossed the Potomac River and marched to Pennsylvania. The Union Army of the Potomac, under its new commander, General George G. Made, marched to intercept General Lee.
On Wednesday, July 1, two divisions of Confederates headed to Gettysburg. They ran into Federal cavalry West of the town at Willoughby Run and the battle began. Events quickly escalated. General Lee rushed 25,000 men to the scene, however the Union had less than 20,000 men. .
After a long period of aggressive fighting and heavy casualties on both sides, the Federals were pushed back to the town of Gettysburg and regrouped south of the town along the high ground near the cemetery. General Lee ordered Confederate General R.S. Ewell to take over the high ground. However, General Ewell hesitated to attack. That gave the Union troops a chance to dig in along Cemetery Ridge and bring in reinforcements with artillery. By the time Lee realized general Ewell had not attacked, it was too late to attempt the attack.
General Made arrived at the area and thought it was an ideal place to do battle with the Rebel army. He expected a massive number of Union soldiers totaling up to 100,000 to arrive and strengthen his defensive position.
General James Lonstreet, who was a Confederate General, saw the Union position as nearly impenetrable and told General Lee it should be left alone. He argued that the Confederate Army should instead move East between the Union Army and Washington, and build a defensive position forcing the Federals to attack them instead.