Here is one more thought about the Battle of Gettysburg. The second day was perhaps the turning point in the battle. Most of the fighting took place on the left side of the Union line near a hill called Little Round Top. General Dan Sickles took his men a half mile out from the Union line leaving Little Round Top undefended. The Confederate army realized that if they captured Little Round Top they could flank the Union army and crush it. The Union army realized this at the last minute and rushed several regiments to Little Round Top. At the end of the Union line was the 20th Maine regiment led by Colonel Joshua Lawrence Chamberlain. The 15th Alabama regiment charged up the hill five times and were repulsed five times. And then came another Confederate attack. With their ammunition low and casualties high, and been given orders to defend the hill at all costs, Chamberlain ordered his men to charge down the hill at the Confederates. His charge was successful, the 20th Maine successfully defended Little Round Top, and the Union eventually wins the battle.
This battle was probably Robert E. Lee’s biggest mistake. The Confederate strategy was always to fight a defensive war because they had a smaller army than the Union. But in this battle, Robert E. Lee chose to take the offensive and attack the Union even though the Union was entrenched on the high ground outside of Gettysburg. Lee’s best commander, General James Longstreet, had suggested to Lee that the Army of Northern Virginia maneuver around the Union army, get between the Union army and Washington D.C., threaten the capital, and then find some good ground to defend and force the Union to attack. Perhaps if Lee had listened to Longstreet, Lee’s invasion of the north would have been successful and the outcome of the war much different. But he didn’t, and the defeat at Gettysburg was the beginning of the end for the Confederates in the Civil War.
The goal of General Robert E. Lee and his Army of Northern Virginia was to take the action from war-torn Virginia onto Northern soil. Fresh off the electrifying victory at Chancellorsville (where his heavily outnumbered army had been caught off-guard), Lee's army was at its peak and probably the greatest fighting force in the world. Lee's confidence (which proved to be overconfidence) in his troops was also high, and his grand plan was to resupply his troops from the plentiful farmlands of Pennsylvania while marching toward Baltimore and Philadelphia. His hope was to eventually march southward back toward Washington in the hopes of capturing the capital. Such a feat would have possibly gained the international recognition from other nations that would have resulted in financial (and possibly military) aid as well as formal recognition as a nation. A series of triumphs could also have ended the war.
However, the vanguard of Lee's troops was surprised in Gettysburg, and Lee was forced to battle the Union forces there. A series of mistakes from his new corps commanders, particularly Lieutenant General Dick Ewell (the late Stonewall Jackson's replacement) on the first day, gave the Federals a solid position to give battle. Lee's army was unable to dislodge the Union troops from their strong positions on the second day, and Lee ordered the disastrous "Pickett's Charge" on the third day.
Although casualties were incredibly high on both sides, Lee's army was shattered, and he was lucky to return to the safety of Virginia soil. His losses were unable to be replaced, whereas the Union had vast numbers of men to reinforce their ranks. Confederate hopes for international recognition and a possible end to the war were ended, and Gettysburg proved to be the turning point of the war. U. S. Grant was soon named supreme commander of Union forces, and he took a more aggressive approach against Lee, who was put on the defensive for the remainder of the war.
Neither side meant to get into a fully battle in the town of Gettysburg, but as it turned out, one of the important things was that the Northern forces had the opportunity to choose the high ground and the Confederates were forced to attack because they were concerned about their supply lines being cut. Even the Southern generals were worried about the setting of the battle and there was a great deal of conflict about what they should do and whether they should retreat.
Pickett's charge was certainly an iconic part of the battle, but the previous two days had already decided much of the battle as the Southern forces wore themselves out in the battles around Little and Big Round Top and in places like the Devil's Den, etc.
My guess is that you will get different answers to this question. In addition to this, I would suggest that if this is for a class and there are notes given by an instructor or a textbook analysis that you have to understand, I would examine these sources first. As a battle in the Civil War, Gettysburg was intense. It took three days to resolve and turned out to be the bloodiest battle in the entire conflict. Combined casualties totaled to over 40,000. When Rhett Butler says, "It's going to be decided in small town in Pennsylvania called Gettybsurg," he isn't kidding. Essentially, the South has made inroads into the North and the progression into Gettysburg was a moment that many Northerners dreaded and about which Southerners felt elated. Both forces meeting on the field in Pennsylvania had fairly decisive consequences. On one hand, the Northern victory came when the Southern forces moved into the center of the Northern stronghold, expecting to overwhelm them. Instead, the Southeners took heavy casualties as they were repelled at Pickett's Charge with rifle fire. This marked the first retreat for the South and helped to define the arc of the war. At the time, not many fully grasped, like Captain Butler, about how the war would play itself out and few understood the historical significance of Gettysburg. Yet, historians in retrospect understood Gettysburg to represent the turning point in the war for there was no other Southern advance into the North and the muscle of the North began to flex more. President Lincoln used the intense battle to deliver his address, which also helped to reconfigure the war's aims and helped to galvanize individuals into action. The Northern campaign had structure and resonance, elements it lacked in full precision until Gettysburg. Combined with the protracted nature of the conflict which greatly benefitted the industrial and more populous North, Gettysburg marked the point where the North was not only repelling, but actually starting the process of advancing into the South. Conversely, it was the last moment of the war where the South was taken as a serious adversary making strides, as opposed to a lumbering giant on the run.