Besides the above reasons, the Romans may likely enough have thought that it was not so much the quantity of the land allotted as its careful cultivation that would make it suffice. It is very necessary, however, that every colony should have common pasturage where all may send their cattle to graze, as well as woods where they may cut fuel; for without such conveniences no colony can maintain itself. CHAPTER VIII.—_Why certain Nations leave their ancestral Seats and overflow the Countries of others_. Having spoken above of the methods followed by the Romans in making war, and related how the Etruscans were attacked by the Gauls, it seems to me not foreign to these topics to explain that of wars there are two kinds. One kind of war has its origin in the ambition of princes or republics who seek to extend their dominions. Such were the wars waged by Alexander the Great, and by the Romans, and such are those which we see every day carried on by one potentate against another. Wars of this sort have their dangers, but do not utterly extirpate the inhabitants of a country; what the conqueror seeks being merely the submission of the conquered people, whom, generally speaking, he suffers to retain their laws, and always their houses and goods. The other species of war is when an entire people, with all the families of which it is made up, being driven out by famine or defeat, removes from its former seat, and goes in search of a new abode and a new country, not simply with the view to establish dominion over it, but to possess it as its own, and to expel or exterminate the former inhabitants. Of this most terrible and cruel species of warfare Sallust speaks at the end of his history of the war with Jugurtha, where in mentioning that after the defeat of Jugurtha the movement of the Gauls into Italy began to be noticed, he observes that “_in the wars of the Romans with other nations the struggle was for mastery; but that always in their wars with the Gauls the struggle on both sides was for life_.” For a prince or commonwealth, when attacking another State, will be content to rid themselves of those only who are at the head of affairs; but an entire people, set in motion in the manner described, must destroy all who oppose them, since their object is to subsist on that whereon those whom they invade have hitherto subsisted.