Numbers 2 consists entirely of God giving commandments as to how the Israelite camp should be arranged. From the NIV:
On the east, toward the sunrise, the divisions of the camp of Judah are to encamp under their standard. […]
The tribe of Issachar will camp next to them. […]
The tribe of Zebulun will be next. […]
All the men assigned to the camp of Judah, according to their divisions, number 186,400. They will set out first. […]
[The rest of the tribes are described]
So the Israelites did everything the Lord commanded Moses; that is the way they encamped under their standards, and that is the way they set out, each of them with their clan and family.
It seems strange to me that God would give explicit instructions as to who should be camped next to whom and the order they should be led, when God seems to be unconcerned with trivial details like that for the rest of the journey. For instance, he doesn't give city planning details for the cities that the Israelites eventually rule.
Considering the narrative of Numbers 2, why did God give instructions about the arrangement of the Israelite tribal camps? What purpose did that serve by having God command this arrangement, rather than leaving it up to the personal preference of the tribes to camp wherever they wanted to?