When the Amalekites came against Israel in battle God enlisted Moses to stand on a hill nearby and lift up his hands with his rod.  This act was the way God wanted him to intercede for the people.  He could have prayed privately but in this case his standing on the hill was a demonstration to all that he was their God-appointed leader and was used by God to intercede for them.  And as it happened, when intercession was made by Moses by the lifting of the rod, the battle was victorious for them, but when Moses lowered his hands the enemy had the advantage.

So it is with us.  When those who intercede are strong in prayer we have victory.  When they get tired and stop praying we fail. Hence we need our intercessors to stay strong in the Lord, to keep praying for us all.  Has God called you to stand on a hill and intercede? Or perhaps He has called you to be like Aaron and Hur who helped Moses by holding his hands up?