Naval warfare
Europe, Western Asia, and Northern Africa

While the barbarian invasions of the 4th century and later mostly occurred by land, some notable examples of naval conflicts are known. In the late 3rd century, in the reign of Emperor Gallienus, a large raiding party composed by Goths, Gepids and Heruli, launched itself in the Black Sea, raiding the coasts of Anatolia and Thrace, and crossing into the Aegean Sea, plundering mainland Greece (including Athens and Sparta) and going as far as Crete and Rhodes. In the twilight of the Roman Empire in the late 4th century, examples include that of Emperor Majorian, who, with the help of Constantinople, mustered a large fleet in a failed effort to expel the Germanic invaders from their recently conquered African territories, and a defeat of an Ostrogothic fleet at Sena Gallica in the Adriatic Sea.

During the Muslim conquests of the 7th century, Muslim fleets first appeared, raiding Sicily in 652 (see History of Islam in southern Italy and Emirate of Sicily), and defeating the Byzantine Navy in 655. Constantinople was saved from a prolonged Arab siege in 678 by the invention of Greek fire, an early form of flamethrower that was devastating to the ships in the besieging fleet. These were the first of many encounters during the Byzantine-Arab Wars.

The Caliphate became the dominant naval power in the Mediterranean Sea from the 7th to 13th centuries, during what is known as the Islamic Golden Age. One of the most significant inventions in medieval naval warfare was the torpedo, invented in Syria by the Arab inventor Hasan al-Rammah in 1275. His torpedo ran on water with a rocket system filled with explosive gunpowder materials and had three firing points. It was an effective weapon against ships.

In the 8th century the Vikings appeared, although their usual style was to appear quickly, plunder, and disappear, preferably attacking undefended locations. The Vikings raided places along the coastline of England and France, with the greatest threats being in England. They would raid monasteries for their wealth and lack of formidable defenders. They also utilized rivers and other auxiliary waterways to work their way inland in the eventual invasion of Britain. They wreaked havoc in Northumbria and Mercia and the rest of Anglia before being halted by Wessex. King Alfred the Great of England was able to stay the Viking invasions with a pivotal victory at the Battle of Edington. Alfred defeated Guthrum, establishing the boundaries of Danelaw in an 884 treaty. The effectiveness of Alfred's 'fleet' has been debated; Kenneth Harl has pointed out that as few as eleven ships were sent to combat the Vikings, only two of which were not beaten back or captured.

The Vikings also fought several sea battles among themselves. This was normally done by binding the ships on each side together, thus essentially fighting a land battle on the sea. However the fact that the losing side could not easily escape meant that battles tended to be hard and bloody. The Battle of Svolder is perhaps the most famous of these battles.

As Muslim power in the Mediterranean began to wane, the Italian trading towns of Genoa, Pisa, and Venice stepped in to seize the opportunity, setting up commercial networks and building navies to protect them. At first the navies fought with the Arabs (off Bari in 1004, at Messina in 1005), but then they found themselves contending with Normans moving into Sicily, and finally with each other. The Genoese and Venetians fought four naval wars, in 1253–1284, 1293–1299,1350–1355, and 1378–1381. The last ended with a decisive Venetian victory, giving it almost a century to enjoy Mediterranean trade domination before other European countries began expanding into the south and west.

In the north of Europe, the near-continuous conflict between England and France was characterised by raids on coastal towns and ports along the coastlines and the securing of sea lanes to protect troop–carrying transports. The Battle of Dover in 1217, between a French fleet of 80 ships under Eustace the Monk and an English fleet of 40 under Hubert de Burgh, is notable as the first recorded battle using sailing ship tactics. The battle of Arnemuiden (23 September 1338), which resulted in a French victory, marked the opening of the Hundred Years War and was the first battle involving artillery. However the battle of Sluys, fought two years later, saw the destruction of the French fleet in a decisive action which allowed the English effective control of the sea lanes and the strategic initiative for much of the war.
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