Tribal Encampments

The beginning of this week's parsha discusses the arrangement of the shevatim as they encamped in the midbar, following the census that was taken in the second year of their sojourning. Why is it that this arrangement of the tribes was first set up in the second year of their travels, rather than immediately following Yetzias Mitzrayim?

R' Yaakov Kamenetsky notes in Emes L'Yaakov that the division of the nation into tribal camps highlighted the different skills and special characteristics that made each tribe unique and that were essential to the functioning of the nation as a whole. However, such a division carried with it the danger of encouraging a tribalism that could ultimately divide the people. Hence, the tribal camps were not set in place until the Mishkan was built, which, by standing in the middle of the camp, served as a reminder that the tribes, despite their differences, all have the same focus to their activities, and should find unity in this, as opposed to separation.