But on the western shore lay flourishing Greek cities still independent of Persian rule. Moreover, the coastal towns like Corinth and Athens were developing considerable power on the sea, and it was evident that unless European Greece were subdued it would stand as a barrier between Persia and the western Mediterranean. Darius perceived the situation and prepared to destroy these Greek states before they should become too formidable. The story of this effort, ending at Salamis and Platea, and breaking for all time the power of Persia, belongs in the subsequent chapter that narrates the rise and fall of Athens as a sea power. At this point, it is worth pausing to consider in detail the war galley which the Phoenicians had developed and which they handed down to the Greeks at this turning point in the world's history. The bireme and the trireme were adopted by the Greeks, apparently without alteration, save that at Salamis the Greek galleys were said to have been more strongly built and to have presented a lower freeboard than those of the Phoenicians. A hundred years later, about 330 B.C., the Greeks developed the four-banked ship, and Alexander of Macedon is said to have maintained on the Euphrates a squadron of seven-banked ships. In the following century the Macedonians had ships of sixteen banks of oars, and this was probably the limit for sea-going ships in antiquity. These multiple banked ships must have been most unhandy, for a reversal of policy set in till about the beginning of the Christian era the Romans had gone back to two-banked ships. In medieval times war galleys reverted to a single row of oars on each side, but required four or five men to every oar. [Illustration: GREEK MERCHANT SHIP From Torr, _Ancient Ships_.] At the time of the Persian war the trireme was the standard type of warship, as it had been for the hundred years before, and continued to be during the hundred years that followed. In fact, the name trireme was used loosely for all ships of war whether they had two banks of oars or three. But the fleets that fought in the Persian war and in the Peloponnesian war were composed of three-banked ships, and fortunately we have in the records of the Athenian dockyards accurate information as to structural detail. The Athenian trireme was about 150 feet in length with a beam of 20 feet. The beam was therefore only 2/15 of the length. (A merchant ship of the same period was about 180 feet long with a beam of 1/4 its length.) The trireme was fitted with one mast and square sail, the latter being used only when the wind was fair, as auxiliary to the oars, especially when it needed to retire from battle. In fact, the phrase "hoist the sail" came to be used colloquially like our "turn tail" as a term for running away.