What does Isenberg cite as the motivation for Roman expansion?

Roman expansion is often perceived as simply a quest for glory and empire, but any competent historian will point out that the reasons were more complex.

Economic motives, appeals to Rome to serve as a powerful ally or mediator in intertribal warfare, and the Roman belief in the benefits of civilization were all at work. Again, a comparison with the "empires" and responsibilities of modern-day great powers is thought-provoking.