Psa 33:16-19, 16 The king is not saved by his great army; a warrior is not delivered by his great strength. 17 The war horse is a false hope for salvation, and by its great might it cannot rescue. 18 Behold, the eye of the LORD is on those who fear him, on those who hope in his steadfast love, 19 that he may deliver their soul from death and keep them alive in famine.
The psalmist though not named I believe is David in light of vs 2. He shares great lessons from history and personal experience. Perhaps he is reflecting on Joshua, a mighty man of war whose victory against the Amalekites is credited to Moses on the mountain lifting up his hands in prayers. As long as his hands were up, Joshua and his men were winning but when it went down, they were loosing. (Exo 17). In addition he may have been reflecting on personal experience battling the same enemy, the Amalekites who burned down their camp, captured their families and belongings and fled. David sought God and was assured of victory. He left for battle with 600 men, 200 became weary on the way. Rather than David forfeit the pursuit because of less number, he went after them with 400 and had great victory, (1Sam 30).
God teaches us that though He has endued man with understanding and freedom of will, yet He reserves to Himself the governing authority. The children of men are all under His eyes and all the motions and operations of their souls, which none know but they themselves, He knows better than they themselves, Gen 18:25, “…Shall not the Judge of all the earth do right?”. David was a king, and a man of war from his youth, and yet he acknowledged God to be his only protector and Savior. Let not the strong man then glory in his strength, but let us all strengthen ourselves in the Lord our God, go forth, and go on, in His strength. All the aids are useless without the hand of God giving strength, wisdom, victory. He wants verse 19 to deliver our soul from death and keep us alive in famine. Salvation belongs to our God.