The Fighting Galley
Bryan Waites describes how, both in the Mediterranean and in the Atlantic, the medieval powers of Europe found that the oared galley was a very effective weapon of war.
It is widely believed that the medieval galley was confined almost entirely to the Mediterranean and that the warship of northern waters was a species of round ship—initially a merchantman, adapted for war. The high-castled ships seen in England from the reign of Richard I to the period of Henry V’s adventures in France are taken as typical of all fleets in north-west Europe.
There are many other ideas associated with this—ships manned by sea-soldiers; sea battles fought as land battles; crews made up almost entirely of merchant seamen and a fleet mustered from merchant ships with little planning or preparation shown by those responsible. These are only a few of the ideas that have built up a traditional picture of medieval sea warfare.