I shall adopt as the starting-point of this book the first occasion on which the Romans crossed the sea from Italy. This is just where the History of Timaeus left off; and it falls in the 129th Olympiad. I shall accordingly have to describe what the state of their affairs in Italy was, how long that settlement had lasted, and on what resources they reckoned, when they resolved to invade Sicily. For this was the first place outside Italy in which they set foot. The precise cause of their thus crossing I must state without comment; for if I let one cause lead me back to another, my point of departure will always elude my grasp, and I shall never arrive at the view of my subject which I wish to present. As to dates, then, I must fix on some era agreed upon and recognised by all: and as to events, one that admits of distinctly separate treatment; even though I may be obliged to go back some short way in point of time, and take a summary review of the intermediate transactions. For if the facts with which one starts are unknown, or even open to controversy, all that comes after will fail of approval and belief. But opinion being once formed on that point, and a general assent obtained, all the succeeding narrative becomes intelligible.