Abner had been strengthening his position among the supporters of Saul's dynasty during the war between those on the side of Saul and those on the side of David.
The descendants of Asher, men aged twenty or older, were recorded by name according to the genealogical records of their tribe and families. All those registered who could serve in the army
This was the territory allocated to the tribe of Ephraim, by families. The boundary of their allocation ran from Ataroth-addar in the east to Upper Beth-horon
This was the allocation to the tribe of Manasseh, Joseph's firstborn son. Machir was Manasseh's firstborn son who was the father of Gilead. Because Machir had been an excellent fighter, Gilead and Bashan had already been allocated to him.
So the tribes of Reuben and Gad, and the half-tribe of Manasseh left the rest of the Israelites at Shiloh in the land of Canaan and went home to their land in Gilead that they had received at the Lord's command through Moses.