Joshua 13:1–33 can be divided into two parts:
A description of land that must still be possessed and command to divide the land (Joshua 13:1–7)
The Transjordan distribution for Reuben, Gad and the half-tribe of Manasseh (Joshua 13:8–33)
This chapter begins with a summary of the land that still remains to be conquered (Joshua 13:1–6) followed by a command from God for Joshua to begin distributing the land to the various tribes who will live west of the Jordan River (Joshua 13:7). Before he can do that however, Joshua must first confirm the division of the land on the east of the Jordan River, land which will be inhabited by Reuben, Gad and the half-tribe of Manasseh (Joshua 13:8–33).
1 Now Joshua was old and advanced in years, and the LORD said to him, “You are old and advanced in years, and there remains yet very much land to possess.