In the mid-1400s, western Europe faced a rapidly expanding Muslim power in the east. The Ottoman Empire captured Constantinople in 1453 and over time came to rule, directly or indirectly, much of eastern Europe. Now cut off from direct access to Asian trade via the eastern Mediterranean, Europeans turned south and west in search of new trade routes to India and China. Portugal led the way in the fifteenth century, launching expeditions to explore the west coast of Africa and eventually rounding the tip of Africa and reaching India. After Columbus’s voyages, Spain and Portugal began to explore and conquer the Americas. Portuguese exploration of Africa combined with the establishment of colonial empires in the Americas led to a new era of worldwide trade in African slaves. Through trade, travel, and missionary work, Europeans increasingly came into contact with peoples of whom they had previously had little or no knowledge. For many Europeans, this only reinforced their sense of cultural and religious superiority. For others, it prompted a re-evaluation of basic assumptions about their own society and its place in the world. ■