Politics and War:
Source: Carl von Clausewitz, On War, trans. Col. J.J. Graham. New and Revised edition with Introduction and Notes by Col. F.N. Maude, in Three Volumes (London: Kegan Paul, Trench, Trubner & C., 1918). Vol. 1. Chapter: CHAPTER I: WHAT IS WAR?
This chapter contains Clausewitz's most famous saying about war, that it is the continuation of politics (policy) by other means. Here is the passage in full:
24. WAR IS A MERE CONTINUATION OF POLICY BY OTHER MEANS.
We see, therefore, that War is not merely a political act, but also a real political instrument, a continuation of political commerce, a carrying out of the same by other means. All beyond this which is strictly peculiar to War relates merely to the peculiar nature of the means which it uses. That the tendencies and views of policy shall not be incompatible with these means, the Art of War in general and the Commander in each particular case may demand, and this claim is truly not a trifling one. But however powerfully this may react on political views in particular cases, still it must always be regarded as only a modification of them; for the political view is the object, War is the means, and the means must always include the object in our conception.
It is a truism that in war - old men send young men to die.
And that there are three basic limitations on the human population : disease, starvation, and warfare.
Two of those limiters are poorly operative in developed countries in the modern era.