The Roman thinker and military strategist Vegetius advised the Emperor, "Si vis pacem, para bellum" -- If you want peace, prepare for war.

This is, of course, a paradox. Having spent 60 years of my life studying human nature and his civilisation, 2500 years later I have added one line for that axiom, to reread as,

If you want peace, prepare for war; but, mind you, if you prepare for war, you are most likely to wage it.