An empire is a political unit which exercises control over territory of great extent or a number of territories or peoples through formal annexations or various forms of informal domination.[1]
Empires that are known for conquering much territory with speed include the Greek Macedonian Empire (during the time of Alexander the Great) and the Arab Empire. According to Scottish historian James Buchan: "In speed and extent, the first Arab conquests were matched only by those of Alexander the Great, and they were more lasting."[3]
Sea empires grew mostly by sailing to distant places and conquering them. Mediterranean sea empires were the Phoenician states of Tyre, Sidon and Carthage; the Italian maritime republics of Venice and Genoa. Others were the Chola dynasty of Tamil Nadu in India; the Omani Empire of Arabia; and the Austronesian empires of Srivijaya and Majapahit in Maritime Southeast Asia. The Aztec Empire and the Mongol Empire were land empires.