Chapter 20

David.

A prayer, that God will answer "you" in the day of trouble.  This prayer seems to be addressed to a person - or maybe to the nation, but seems to be to an individual.  It "hopes" that this person's prayers will be answered.  MSB says this chapter is a prayer from the people of Israel about their King-General.  This could make sense as the last verse says "O Lord, save the king."  But it is a psalm of David???  There is a pretty long explanation.  Psalm 20 and 21 are "warfare events".  20 is a prayer offered before battle, 21 comes after.  So the people and soldiers in 20 are praying for their King/General, asking for God to help him with the battle.  This context makes the point of view much more clear.

2022 - This makes good sense chronologically also.  The Chronological Bible inserts this one right after 2 Sam 10 where David sends Joab out to battle against Ammon's new King and his mercenaries from Syria.  All of Ammon AND Syria are defeated in these battles.  This would greatly increase the security of Israel under David, and help consolidate his new position as King.  It would inspire great loyalty with the rank and file of the kingdom because it increases their security immensely.