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image: The Battle of Sluys, 1340, from Jean Froissart’sChronicles

In the Mediterranean, naval warfare in the medieval period resembled that of the ancient period: fleets of galleys would exchange missile fire come alongside for marines to fight on deck. This mode of naval warfare continued even into the early modern period, as, for example, at the Battle of Lepanto. Famous admirals included Andrea Doria, Hayreddin Barbarossa, and Don John of Austria.

However, galleys were fragile and difficult to use in the cold and turbulent North Sea and northern Atlantic, although they saw occasional use. Bulkier ships were developed which were primarily sail-driven, although the long lowboard Viking-style rowed longship saw use well into the 15th century. Ramming was impractical with these sailing ships, but the main purpose of these warships remained the transportation of soldiers to fight on the decks of the opposing ship (as, for example, at the Battle of Svolder or the Battle of Sluys).

Warships resembled floating fortresses, with towers in the bows and at the stern (respectively, the forecastle and aftcastle). The large superstructure made these warships quite unstable, but the decisive defeats the more mobile but considerably lower boarded longships suffered at the hands of high-boarded cogs in the 15th century ended the issue of which ship type would dominate northern European warfare.

In the medieval period, it had proved difficult to mount cannons on board a warship, although some were placed in the fore- and aftcastles. Small hand-held anti-personnel cannons were used, but large cannons mounted on deck further compromised the stability of warships, and cannons at that time had a slow rate of fire and were inaccurate.

All this was about to change at the end of the medieval period. The insertion of an opening in the side of a ship, with a hinged cover, allowed the creation of a gundeck below the main deck. The weight of cannon distributed to lower decks of the ship increased its stability immensely, effectively providing ballast, and a row of cannon on a lower deck produced thebroadside, where the weight of shot overcame the inherent inaccuracy of firing cannons from a ship at sea. An example is the Mary Rose, the flagship of King Henry VIII’s fleet, which had around eleven heavy guns per side, all of which were capable of firing shot nine pounds or more.

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(via cassandra879)