Civilizations in Egypt, Mesopotamia, and along the Mediterranean Sea, historic Yemen became an important overland trade link between these civilizations and the highly prized luxury goods of South Arabia and points east and south. As a result, several pre-Islamic trading kingdoms grew up astride an incense trading route that ran northwest between the foothills and the edge of the desert. First, there was the Minaean kingdom, which lasted from about 1200 to 650 bc, and whose prosperity was due mainly to the trade of frankincense and spices. The large and prosperous kingdom of Saba’ (Sheba), founded in the 10th century bc and ruled by Bilqis, the queen of Sheba, among others, was known for its efficient farming and extensive irrigation system built around a large dam constructed at Ma‘rib. Farther south and east, in the region that would later become South Yemen.

The Romans began expanding their power and influence into the Red Sea in the 1st century AD and soon learned the secret of the Yemeni traders: how to exploit the monsoon winds to traffic between the Red Sea and southern Asia. It was then only a matter of time before Yemeni prestige began to dwindle, since they could not effectively compete against imperial Rome. The resulting economic decline made it impossible for the Yemeni states to maintain their extensive cities and attendant facilities; the most famous instance was the failure to maintain the Great Dam at Ma'rib—the heart of a monumental irrigation project and one of the engineering marvels of the ancient world. Its rupture in AD 525 constitutes the symbolic end to the ascendancy of the Yemeni empires.

The Islamic era, which began in the 7th century, contains many events critical to the formation of Yemen and the Yemeni people. The force with which Islam spread from its origins in Mecca and Medina in the nearby region of Al ?ijaz (the Hejaz) led to Yemen’s rapid and thorough conversion to Islam. Yemenis were well-represented among the first soldiers of Islam who marched north, west, and east of Arabia to expand Muslim territory. Yemen was ruled by a series of Muslim caliphs, beginning with the Umayyad dynasty, which ruled from Damascus in the latter part of the 7th century; Umayyad rule was followed by the Abbasid caliphs in the early 8th century.