I've been meaning to post this for a little while- it's a piece for the December issue of The Atlantic. The article is a review of the Mary Beard book SPQR: A History of Ancient Rome. As the review explains, the book details just how important the idea of citizenship was to the empire. As opposed to the way many nations today make becoming a citizen a daunting process, the Romans expanded citizenship across the empire, to the peoples not only not living in Rome, but who might not even speak Latin.
Absorbing the villages and tribes they conquered, instead of completely razing and destroying them, strengthened the empire. By making these conquered peoples Roman citizens, they expanded their territory, their tax base, and the pool from which they could draw more soldiers.
The full page:
Pick up a copy of The Atlantic, and check out the article. And then pick up Beard's book, SPQR, if you're a history buff. Thank you to Kara, my AD on this!