Why did the union win Battle of Gettysburg?

Answer 1

Chance.

A Confederate officer managed to lose a copy of Lee's orders.

They were found by Union soldiers and shown to McLellan, who saw that Lee had divided his army into widely-separated divisions.

McLellan might have been able to destroy these divisions, one by one. But there had been a Confederate spy in the camp, who alerted Lee, who then concentrated his troops at Antietam Creek, by Sharpsburg.

The Union still won the battle, but was not able to destroy the Confederate army, which escaped back to Virginia.

Answer 2

The Union commanded the high ground with superior numbers. The Confederates were forced to attack uphill after advancing over open fields, subject to cannon and rifle fire for most of the way.

IMPROVEMENT.

1 - Lee was forced to give battle before he was ready to do it.

2 - During the two first days of the battle Lee's knowledge of the enemy power and deployment had been seriously crippled by the absence of his cavalry force, which was off, with his leader, Gen. Stuart, on an irresponsible raid to the East.

3 - During the battle the Union units could operate through internal lines.

4 - Lee decided to order the great charge of July 3rd in spite of the contrary opinion expressed by James Longstreet. It was a great mistake committed by Lee, who overestimated the striking power of the mass ( the 15 000 men appointed to the assault), against the stopping power of the, grazing, standing barrage fire of the defenders' rifled guns and artillery.

5 - During the artillery duel that preceded the assault, the chief of Union artillery, Gen. Hunt, managed to held silent some 40 cannons and to react to the Confederate fire in a intermittent way, giving to the enemy the impression that a large part of the Federal batteries had been destroyed by their fire. Thus the commander of Confederate artillery Colonel Alexander, gave to Longstreet the green light for the assault to be carried, with the consequent well known consequences.

Answer 3

The Union held the high ground. From day two on it had superior numbers and superior logistics as well as superior position. Federal forces were fighting on their own turf and were determined not to give ground. Though Meade did not have Lee's brilliance, he was fighting on the defensive, which is usually easier, and made no major mistakes. Lee risked a frontal assault uphill against a well entrenched force after crossing an open field, almost certain to fail given the enemy's superior position and firepower.