I am studying up on the Battle of Gettysburg. Some of the battle is a bit confusing. Just wondering if you could explain how the Union gained the advantaged and pulled ahead when at first it seemed like they were going to lose.
The Union army was slower getting its troops to the field. However, it was able to get to the high ground first. Before there was air power, holding the high ground was important since it forced the enemy to charge up a hill to attack you. This would slow them down and make the attack more difficult.
There is a famous story on the second day of the 20th Maine defending a hill called Little Round Top. The Regiment held the ground against repeated assaults and was running out of ammunition. Many commanders would have retreated. But instead, the Union commander ordered a bayonet charge down the hill, capturing many of the Confederates and forcing the rest to withdrawal. If that hill had been lost on the second day, the Battle's outcome could have been quite different.
Throughout the battle, the Confederates were on offense, and the Union on defense. This is the opposite of most battles of the war. On the third day, Gen. Lee ordered a direct assault on the Union center. This was a highly risky maneuver since marching thousands of men across a field into lines of canon could be catastrophic. Lee had ordered his cavalry to circle around and disrupt the Union line from the rear. He hoped the confusion of being attacked by both sides would cause the Union line to become frightened and break. However the cavalry was stopped before they made it and never attacked the line. Therefore, the Confederate infantry marched right into a strong line of defense and was devastated. After such losses, the Confederates had not choice but to withdraw.
In short, the Union won because it maintained a strong defense, held the high ground, and did not break in the face of repeated assaults (as it had in earlier battles). Experienced veteran soldiers and officers were an important key to this. It forced the Confederates to take a big gamble at the end, which they also lost in a big way.
I hope this helps!