2 Samuel 17:25
And Absalom made Amasa captain of the host instead of Joab: which Amasa was a man’s son, whose name was Ithra an Israelite, that went in to Abigail the daughter of Nahash, sister to Zeruiah Joab’s mother. And Absalom made Amasa captain of the host instead of Joab: which Amasa was a man’s son, whose name was Ithra an Israelite, that went in to Abigail the daughter of Nahash, sister to Zeruiah Joab’s mother.
Hushai's counsel had gained David opportunity for escape, and the impatient Absalom soon set out in pursuit of his father. At the time Absalom made the appointment, David was at Mahanaim. Mahanaim had been the royal seat of Ishbosheth. It was a strongly fortified city surrounded by a mountainous district favorable for retreat in case of war. It lay in a well-provisioned country among people friendly to David's cause. There many adherents joined David, while wealthy tribesmen brought abundant gifts of provision and other needed supplies.
Absalom passed over Jordan with all the men of Israel with him. He made Amasa commander-in-chief of his forces instead of Joab. Amasa was the son of David's sister Abigail. The army under Amasa was large but undisciplined and poorly prepared to cope with the tried soldiers of his father.