Triera is the main type of a battle ship of the Mediterranean period of the Greek-Persian wars (V-IV centuries BC). The main weapon of the triera was a copper bind ram, the extension of the keel beam. The speed of the ship on oars was up to 18 km/h. The triera had a big square sail and a small sail on the inclined mast in the bow part. The masts were removable. In the course of a battle the triera accelerated and thus could break oars of an enemy ship stopping it. Than it used its ram. The crew of the ship had more than 200 men including oarsmen, sailors and heavily armored hoplites.