Who, according to Lincoln, has hallowed (made holy) the battlefield ground?

The soldiers who died on the battle field

Explanation:

Lincoln continued fighting the Civil War, despite all the bloodshed and loss of life, because he believed that losing the war meant nothing less than the failure of the American experiment in republican government.

Lincoln wrote and delivered the Gettysburg Address for the people of the American colonies understand that the civil war is destroying the simple ideals that their nation had been built upon

Of these casualties, 7,058 were fatalities (3,155 Union, 3,903 Confederate). Another 33,264 had been wounded (14,529 Union, 18,735 Confederate) and 10,790 were missing (5,365 Union, 5,425 Confederate). At field hospitals around Gettysburg, amputated limbs lay in heaps and were buried together.