As dawn broke over Gettysburg, Pennsylvania, on July 1, 1863, the fate of the United States teetered on a razor's edge. The Confederate Army of Virginia, commanded by General Robert E. Lee, had just won a massive victory at Chancellorsville, Virginia, and was now marching through Union territory. The Union Army of the Potomac was the only thing standing between Lee and the Union capital, Washington, DC. Commanding the Union forces was newly promoted General George Meade, who replaced General Joseph Hooker after his defeat at Chancellorsville.
The Confederate cause was on the brink of success. A victory in Union territory would leave DC exposed and had the potential to cause France and Great Britain to recognize the Confederacy internationally. These factors, combined with strengthening sentiment in the North to end the conflict, could ultimately force Abraham Lincoln to concede the independence of the Confederate States. It seemed that, with a single victory, the South could win the conflict.
On that sunny, summer morning, Meade was attempting to keep his troops between Lee and the capital. He sent his cavalry, led by General John Buford, ahead to scout. Meanwhile, Lee's troops, organized into three corps, were attempting to meet at South Mountain, where they would be in a strong position to either defend or attack. The three corps were led by General Richard S. Ewell, General A.P. Hill, and General James Longstreet. The Confederate Cavalry was led by General J.E.B. Stuart, and had gone on a raid behind the Union troops. The two opposing forces would meet at Gettysburg, where over three days of intense battle, history would be made.
By the time the dust settled on the fourth day, 11,000 men had perished, 29,000 were wounded, and 10,000 were missing. However, the Union troops remained, and the Confederate troops were retreating back to Virginia. How did Meade's Army of the Potomac manage to win this crucial victory over a Confederate force led by one of the most brilliant generals in American history?
As fighting raged to the northwest of Gettysburg on the first day, Union forces arrived on Cemetery Hill just to the southeast of the town. Instead of pushing forward to join the fight, the Union chose instead to secure the high ground, which was the most defensible position.
This decision would set the stage for the next two days of fighting, where the Union would try to hold this tactical advantage against Confederate attacks. The Union forces arranged themselves in a fishhook shape along Cemetery Ridge, Culp's Hill, Little Round Top, and Big Round Top.
On July 2, 1863, at the extreme left flank of the Union line, the 20th of Maine under Colonel Joshua Chamberlain was positioned on Little Round Top. His orders were to hold the position at all costs. The battle raged throughout the day, and the regiment was running out of ammunition. As the Confederates began another attack on the position, Chamberlain ordered his troops to fix bayonets and charge. The desperate charge worked, and the Confederates either surrendered or withdrew.
It should be noted that Chamberlain wasn't the only Union officer to lead a desperate charge to save Little Round Top. Earlier in the day, Colonel Patrick O'Rorke led his 140th New York into a separate charge and engaged the Confederates hand to hand. Unlike Chamberlain, O'Rorke did not survive the heroic maneuver.
Before the Battle of Gettysburg commenced, Stuart had taken the Confederate cavalry on a long sweep to position it between the Union forces and Washington, DC. Stuart's orders were to screen for Lee's troops, but instead, Stuart went off on a raid and was subsequently delayed. This left the main force of the Confederates, already positioned deep inside enemy territory, without any cavalry.
The importance of this was twofold. First, without Stuart's cavalry, the Confederate forces lacked intelligence data. Without the means to properly scout enemy positions, General Robert E. Lee was left guessing what the enemy was doing during critical moments in the battle. Second, without Confederate cavalry available on the first day of the battle, General John Buford's Union cavalry was able to delay the Confederates long enough for initial reinforcements to arrive.
Stuart's cavalry didn't arrive until July 2, the second day of the battle. By then, they were already exhausted from the journey.
At 1:00 pm on the third day, in preparation for what would become known as Pickett's Charge, Lee ordered a massive cannonade on the Union fortifications.
Around 150 cannons were used in the operation before Pickett's men began their advance. However, the artillery bombardment was largely ineffective, as much of it sailed over the Union position.