Byzantine Empire
Navy

The navy dominated the eastern Mediterranean and were active also on the Black Sea, the Sea of Marmara, and the Aegean. Imperial naval forces were restructured to challenge Arab naval dominance in the 7th century, and would later cede its own dominance to the Venetians and Genoans in the 11th century. The navy's patrols, in addition to chains of watchtowers and fire signals that warned inhabitants of threats, created the coastal defense for the Empire and were the responsibility of three themes (Cibirriote, Aegean Sea, Samos) and an imperial fleet that consisted of mercenaries like the Norsemen and Russians that later became Varangians.

A new type of war galley, the dromon, appeared early in the sixth century. A multi-purpose variant, the chelandia, appeared during the reign of Justinian II (r. 685–711) and could be used to transport cavalry. The galleys were oar-driven, designed for coastal navigation, and are estimated to be able to operate for up to four days at a time. They were equipped with apparatus to deliver Greek fire in the 670s, and when Basil I (r. 867–886) developed professional marines, this combination kept a check on Muslim raiding through piracy. The dromon were the most advanced galleys on the Mediterranean, until the 10th century development of a dromon called a galeai and which superseded dromons with the development of a late 11th century Western (Southern Italian) variant.
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