I see the above quote is credited to Byron in the main quotation site, and true enough it's a line from The Bride of Abydos, but it was already 1700 years old when Byron quoted it there. It first appeared in the historian Tacitus' life of his father-in-law Cnaeus Julius Agricola, the general who completed the Roman conquest of Britain. Agricola took Roman arms right into the heart of the Scottish Highlands and brought the Caledonians to battle at a place called Mons Graupius. On the eve of battle the Caledonian leader Galgacus made, Tacitus tells us, a speech to his warriors which included this passage:

The Romans, by a strange singularity of nature, are the only people who invade, with equal ardour, the wealth and the poverty of nations. To rob, to savage, and to murder, in their imposing language, are the arts of civil policy. They make a solitude, and call it peace (Solitudinem faciunt; pacem appellant).

Tacitus then goes on to tell us that the ensuing battle was a complete slaughter of the Caledonians. So how could he possibly know what Galgacus said? Simple - he was just making use of the privilege, claimed by every Roman historian, of making up his characters' speeches. To sum up: I would list it under Tacitus, not Byron.

Thank you very much for the clarification, I'll change it the next time I update the site.
(and the same goes for the "love and war" quote)