Speak with Jaina in front of the gates of Orgrimmar. Part of this quest happens in Durotar, Durotar, Boralus, The Dranosh'ar Blockade and Orgrimmar.
"No matter what doubts he harbored, Saurfang was an honorable soldier. He prevented both a civil war within the Horde and the potential destruction of the Alliance. He brought an end to Sylvanas's reign and saved many lives at the cost of his own. We shall honor his sacrifice".
Upon completion of this quest you will gain 10 250 experience and will learn Battlefield Commendation.
Here you can buy Old Soldier boost for EU or US Servers.
You'll get guide for completing Old Soldier boost