People throughout the Eastern Hemisphere have spent much of the 1400's recovering from the effects of the plague and Mongol empire-building in the previous century. Ming rulers have brought stability and prosperity to China and have begun constructing a great defensive wall to keep nomadic invaders out. The Ottoman Empire has been expanding rapidly, filling the vacuum created in the Islamic world by the sudden death of the Mongol leader Timur and the subsequent collapse of his Empire. The Ottomans completed their century-long conquest of the Byzantine Empire by capturing Constantinople. The population is climbing throughout the Eastern Hemisphere.

Merchants and princes in Western Europe have been searching diligently for ways to establish fresh trade relations with Asian lands. Most Asian goods reach Europe through Venetian trading houses. But the Venetians' prices are very high because they obtain the goods from Muslim traders, who act as middlemen and take their own profits from the sale. Portuguese explorers recently found a sea route to India. In addition, under the sponsorship of the Spanish crown, the Genoese mariner Christopher Columbus has now made his third voyage westward to find a sea route to Asia.

Meanwhile, in the Americas, two dynamic imperial states have undergone rapid expansion. One power in central Mexico has grown from a small state centered on the city of Tenochtitlan to the dominant power in Central America. And from its center at Cusco, the Inca Empire has extended its authority over a vast territory in Andean South America.