He is speaking to the kingdoms of Judah and Israel. Their warfare was hard service.
The Lord had already secured His exaltation. He has been rewarded. Also, I think His reward could be those that come with Him in the first resurrection. They act as his arm, and rule for them.
With the Lord's glory, and majesty, the earth is so small along all His works. Even burning all the cedars in Lebanon would not begin to be a worthy sacrifice unto Him.
The Lord never gives up on us. :)
Even the young ones, with so much energy and enthusiasm do not have the strength to stand against all.