This phrase is used here to mark the beginning of a new part of the story. If your language has a way for doing this, you could consider using it here.
This is background information from the author. It was harder to fight wars in the cold winter, so kings normally waited for spring to attack their enemies. (See: [[rc://en/ta/man/jit/writing-background]])
Here "kings" is a metonym that means the kings sent their armies into battle. Joab was the commander of David's army. Alternate translation: "kings normally send their armies to war ... Joab led David's army into battle" (See: [[rc://en/ta/man/jit/figs-metonymy]])
"He" refers to the soldiers as well as Joab. Alternate translation: "Joab and his soldiers surrounded Rabbah" (See: [[rc://en/ta/man/jit/figs-metonymy]])