Who is Lincoln talking about when he says We cant forget what they did here?

When Lincoln says, "We can't forget what they did here," he is referring to the soldiers who fought and died during the Civil War, particularly in the context of the Gettysburg Address. He emphasizes the sacrifices made by these individuals in the struggle for the nation's ideals, specifically liberty and equality. Lincoln's remarks serve to honor their memory and reinforce the importance of continuing the fight for those principles.