The earliest code of naval signals is that drawn up in the ninth century A.D. by the Emperor Leo VI in his treatise on Tactics[344]. Leo in the Introduction to his nineteenth chapter explains that he has been unable to find anything on this subject among ancient Greek writers except a few scattered references and that his knowledge is mainly derived from the experience of his Generals. In this nineteenth chapter, which deals with Naval Warfare (Περὶ ναυμαχίας [Greek: Peri naumachias]) he says: 39. Let there be some standard (σημεῖον [Greek: sêmeion]) in your ship, either a banner (βάνδον [Greek: bandon]) or a streamer (φλάμουλον [Greek: phlamoulon]) or something else in some conspicuous position, to the end that you may be able, thereby, to make known what requires to be done, and that the rest may set themselves to carry out the course of action decided on, whether it be to fight or to withdraw from fighting; to open out to surround the enemy, or to concentrate to the relief of an endangered portion of the fleet; to slow the rowing or increase speed; to make an ambush, or, emerging from ambush to attack the enemy; or, in general, whatever the signal that has its origin in your ship, that the others, by keeping an eye on her, may be able to execute it. 40. For in such an emergency you will not be able to make use either of the voice or of the trumpet to communicate what is necessary, because of the uproar and the tumult, and the sound of the sea, and the crash of ship against ship, the noise of the oars, and above all the clamour of the combatants. 41. Further, let the signal be given by setting the standard upright or by inclining it to the right or to the left, or by moving it twice to the right or left, or by shaking it, or lifting it up, or lowering it or altogether withdrawing it or altering its position, or by varying the appearance of the head by means of devices or colours as was the practice amongst the ancients; for in time of war they gave the signal for battle by raising what was called the Phoinikis (φοινικίδα [Greek: phoinikida]). There was also what was called the "cap" (μαμελαύκιον [Greek: mamelaukion]) raised upon a pole, red in colour, and they had some other signals which were made known in like manner. Perhaps however it would be safer to make your signals by your own hand. 42. And thus, O General, let the exercise of these signals be practised, so that all the officers in command of ships under you may have certain knowledge of all such signs; of the reason why each is made, and when, and how, and may not fail. So that, well familiarised with the signals, they may readily understand them in time of emergency and carry out the orders indicated.