Sultan Mehmed IV wrote the following letter to the Cossacks: “Sultan Mehmed IV to the Zaporozhian Cossacks As the Sultan; son of Muhammad; brother of the sun and moon; grandson and viceroy of God; ruler of the kingdoms of Macedonia, Babylon, Jerusalem, Upper and Lower Egypt; emperor of emperors; sovereign of sovereigns; extraordinary knight, never defeated; steadfast guardian of the tomb of Jesus Christ; trustee chosen by God Himself; the hope and comfort of Muslims; confounder and great defender of Christians — I command you, the Zaporogian Cossacks, to submit to me voluntarily and without any resistance, and to desist from troubling me with your attacks.” The Cossacks, not to be out-done sent the following reply: “Zaporozhian Cossacks to the Turkish Sultan O sultan, Turkish devil and damned devil’s kith and kin, secretary to Lucifer himself, Greetings! What the devil kind of knight are you, that can’t slay a hedgehog with your naked arse? The devil excretes, and your army eats. You will not, you son of a bitch, make subjects of Christian sons; we’ve no fear of your army, by land and by sea we will battle with thee, fuck your mother. You Babylonian scullion, Macedonian wheelwright, brewer of Jerusalem, goat-fucker of Alexandria, swineherd of Greater and Lesser Egypt, pig of Armenia, Podolian thief, catamite of Tartary, hangman of Kamyanets, and fool of all the world and underworld, an idiot before God, grandson of the Serpent, and the crick in our dick. Pig’s snout, mare’s arse, slaughterhouse cur, unchristened brow, screw your own mother! So the Zaporozhians declare, you lowlife. You won’t even be herding pigs for the Christians. Now we’ll conclude, for we don’t know the date and don’t own a calendar; the moon’s in the sky, the year with the Lord, the day’s the same over here as it is over there; for this kiss our arse! Koshovyi Otaman Ivan Sirko, with the whole Zaporozhian Host.”
There's a famous 19th century painting imagining the Cossacks writing this reply and having a grand old time.
I like the original Laconic reply. Phillip of Macedon threatened to invade Sparta (inhabitants of Laconia, hence "laconic"). His first message was to ask them whether he should come as friend or foe. The Spartans replied "Neither". Irritated, Phillip sent a threat. "If I invade Laconia, I shall turn you out." The Spartan reply was as follows: "If." Unfortunately, Phillip followed up on his threat and invaded.