Answer:
Lincoln implies the fact that they (he and the observers) cannot do much to make sacred or dedicate the fields of battles of the civil war (American civil war), to those living or dead that fought for the retention of the United states as a single country.
Step-by-step explanation:
Lincoln at the Gettysburg Address, meant to dedicate a portion of the fields of battle as a final resting-place for those who gave their lives, and those who fought for the nation, was trying to point out the fact that even as much as they try to dedicate these fields in memory of those who fought, and those who died for America in the war, the mere sacrifice of these people alone has made these fields more sacred than they can try to make these fields.