Darius, king of the Persians, and his reaction when the Ionian and Athenian Greeks burned one of his cities:

When Darius first heard this report, he disregarded the Ionians, since he knew that they at least would not escape punishment for their revolt; but he inquired who the Athenians were, and after he had been told, he asked for a bow. He took the bow, set an arrow on its string, and shot the arrow toward the heavens. And as it flew high into the air, he said: "Zeus, let it be granted to me to punish the Athenians." After saying this, he appointed one of his attendants to repeat to him three times whenever his dinner was served: "My lord, remember the Athenians." ^*

I fucking love every second of this. Imagine this shit in a modern context:
Obama: Malia, pass the potatoes, please.
Some aide: Mr. President, remember the Russians.
Michelle: Honey, are we meeting the French president next week?
Some aide: Mr. President, remember the Russians.
Sasha: Dad, do I have to walk Bo tonight?
Some aide: Mr. President, remember the Russians.

^* Herodotus, The Histories, trans. by Andrea Purvis, ed. by Robert Strassler (New York: Anchor Books, 2007): 415-16.