In terms of grammatical structure, it is important to note that 2 Samuel 20 is a narrative with common elements. These include characters, plot structure, protagonists-heroes and antagonists-villains, an introduction, rising action, climax, falling action, conclusion, imagery, etc. Everyone has a historical story that impacts their life. Who are the heroes and villains in this story and in your story?
In historical context, Absalom’s death did not end the tribal tensions within Israel [19:40-43]. David’s return to Jerusalem caused Sheba, to call for a revolt. Sheba was from the tribe of Benjamin; the same tribe as Saul. Many Israelites A joined Sheba in the rebellion, while the men of Judah remained loyal to their tribe member David [vv.1-2].
Absalom had set Amasa over his army [17:25], but after Absalom was slain, David offered to make Amasa commander of the army in place of his long-term commander Joab [19:13]. After returning to his palace in Jerusalem, David instructed Amasa to recruit an army from the men of Judah within three days and report back to David [vv.4-5].
Amasa failed to return within three days with soldiers, possibly because of distrust in Judah over his previous defection to Absalom. David then ordered Abishai and Joab and Ittai to proceed with men they recruited. Amasa joined the group, but Joab used the opportunity to kill Amasa, either because he considered him an enemy or a competitor or both [vv.5-13]. Joab had murdered Abner about 15 years before [2 Samuel 3] [to the embarrassment of David], Uriah [at David’s request], Absalom [David mourned his death] and now Amasa.
Which of the four main characters are the antagonists-villains or protagonists-heroes? Why do you think Joab killed Amasa? What is the message for you today?
Notes: A- “Israel” is used in three ways:  for the 12 tribes of Israel that were united under Joshua, David and Solomon,  for what is known as the northern tribes without Judah and sometimes Benjamin and  the area occupied by the people returning from captivity by Babylon and Persia and the government formed in May 1948. For Tribal map of Israel in time of Joshua click here; and David and Solomon click here, the timeline in the upper left corner is very badly off.