Absalom appointed Amasa to take Joab’s place as commander of the army. (Amasa was the son of a man named Ithra, a descendant of Ishmael. His mother was Abigail, the daughter of Nahash and sister of Joab’s mother Zeruiah.)
The lot was drawn for the tribe of Manasseh, because Manasseh was Joseph’s firstborn. Machir, Manasseh’s firstborn, the ancestor of the people living in Gilead, had received Gilead and Bashan because he was a soldier.