Lincoln gave the Gettysburg Address in November 1863, four and a half months after the battle of Gettysburg, which was fought in July, 1863. The event being commemorated was the dedication of a cemetery to fallen soldiers on the site. Lincoln's speech followed a two-hour oration by Edward Everett. Lincoln's address lasted only a few minutes.

Lincoln's short speech addresses three main issues: the cause for which the soldiers died, the dedication of the cemetery, and the need to continue the struggle to win the war.

Lincoln notes that the fallen soldiers gave up their liberty to preserve a nation that began eighty-seven years before as a radical experiment in liberty. He appeals to the potential fragility and value of the American vision when writes,

Now we are engaged in a great civil war, testing whether that nation, or any nation so conceived and so dedicated, can long endure.

Second, Lincoln notes that they are all here to consecrate a portion of the battlefield as a burial ground for soldiers who fell in battle:

We have come to dedicate a portion of that field, as a final resting place for those who here gave their lives that that nation might live.

The longest part of the short speech, however, is dedicated to reminding listeners of the importance of continuing the struggle to preserve the nation so that the soldiers who died would not have died in vain. The soldiers died there to preserve not only a nation but a great experiment in freedom, one that Lincoln hopes will have a rebirth into greater freedom rather than "perish from the earth":

It is rather for us to be here dedicated to the great task remaining before us—that from these honored dead we take increased devotion to that cause for which they gave the last full measure of devotion—that we here highly resolve that these dead shall not have died in vain—that this nation, under God, shall have a new birth of freedom—and that government of the people, by the people, for the people, shall not perish from the earth.

In his short but powerful speech at the dedication of the Soldier's National Cemetery at Gettysburg, Pennsylvania, President Abraham Lincoln deftly addressed three issues: the soldiers, the nation, and the cemetery.

The occasion of the speech was to dedicate the cemetery. Lincoln notes that the land was the scene of "a great battle-field of that war," that is, the Civil War. Although he concedes that it is "fitting and proper" to set apart a portion of the battlefield as a "final resting place" for the soldiers who died there, he insists the ground is already hallowed because of their actions.

Lincoln goes on to honor the soldiers who fought for the Union in the Battle of Gettysburg. He thanks them for giving their lives so that the nation could live. He praises them and the soldiers who survived, asserting that "the brave men, living and dead, who struggled here" are the ones who have consecrated the ground more than any speaker could. Their work in trying to save the Union was noble, and it will never be forgotten.

As president, Lincoln's primary concern at the time was the survival of the nation. He uses the address to reaffirm the importance of the United States of America as a complete union. He refers to the founding of the country, citing the Declaration of Independence, which documented "the proposition that all men are created equal." He describes the Civil War as a war that is:

testing whether that nation, or any nation so conceived and dedicated, can long endure.

This reference to the overarching goals of the nation put the cemetery and the soldiers into perspective. A much larger issue was at stake—namely, the very foundation of our political experiment in democracy. Thus, he ends the speech with an eloquent appeal to his listeners to do what they can to keep the nation intact:

that we here highly resolve that these dead shall not have died in vain—that this nation, under God, shall have a new birth of freedom—and that government of the people, by the people, for the people, shall not perish from the earth.

Lincoln's address discussed the cemetery, the soldiers, and the nation, but it focused on the essential task of keeping the country unified.

1) The nation was founded "four score and seven"—that is to say, 87—years ago according to the belief that all men are equal, as set out clearly in the Declaration of Independence.

2) Those brave men who died at Gettysburg gave their lives for the principle of equality enshrined in the Declaration. For many of Lincoln's auditors, this will have come as something of a surprise, because to most people, the Civil War was being fought to preserve the Union.

3) In any case, the sacrifice that these men made will ultimately have been for nothing if the end of the Civil War doesn't give rise to a "new birth of freedom." What Lincoln is doing here is announcing a change in war aims, from preserving the Union as it was before the War to building a whole new one on the basis of a radicalized reworking of the Founding Fathers' commitment to equality. From now on, equality won't just be formal, it'll be substantive.

Lincoln began by noting that the nation had been born 87 years earlier "conceived in Liberty and dedicated to the proposition that all men are created equal."  The civil war, he said, was a test of whether a nation based on those principles could survive.

He then goes on to laud the sacrifice of those who had fought in the war, and said the living must dedicate themselves to giving the nation "a new birth of freedom" and ensuring that "government of the people, by the people, and for the people shall not perish from the earth."

As you can see, there is really one main issue here.  Can a free and democratic nation survive?  You could treat each of the principles he cites as a separate issue -- freedom, equality, and democracy.

1. Lincoln begins this speech by referring to how the nation began, as a county "dedicated" to the idea that all men are equal".
2. This sets the context for his discussion of the Battle of Gettysburg and the great sacrifice that the men who fought there had made. Their sacrifices had greatly contributed to the original idea of the founders of the nation.
3. Finally, he notes that those who remain must continue to fight on so that the nation founded on the premise that "all men are created equal" will not "perish from the earth."