It's difficult for the Westerner to understand one of the great problems that faced those in the Ancient world - the threat of impending war.  In a moment, your house, your property, your food supplies, even your family could be taken from you by an invading army or a band of thieves.  The people looked to their King to provide this protection, this salvation.  In Psalm 110, we encounter God's promise of one such powerful King.  He would exercise divine power across the whole world, subduing enemies under his feet.  Judgment would fall upon the enemies of God's people.  Evil would be avenged when the King took Zion's throne.  But, unlike all the Kings and Priests under the Old Covenant, this King would also be a Priest.  He would personally offer sacrifice in the holy place and intercede for God's people.  In other words, he would be a royal priest after the order of Melchizedek, the one who conferred a blessing upon father Abraham (Gen. 14:17-20).  The great hope of the Jews was that salvation would come through a powerful, priestly King - one that would subdue their enemies and bring blessing to Abraham's offspring.