The "Age of Discovery" from 1450 to 1650 lead to a new age of ocean travel, increased migration, and economic, political, and cultural expansion. First, the outward expansion of Europe began with the Viking voyages, and then the Crusades, but the presence of the Ottoman Turks in the East frightened the Europeans and forced their attention westward. Second, political centralization in Spain, France, and England prepared the way for expansion. Third, the Portuguese, under the leadership of Prince Henry the Navigator, pushed south from North Africa. By 1500 Portugal controlled the flow of gold to Europe and Diaz da Gama and Cabral established trading routes to India. The Portuguese then gained control of the Indian trade by overpowering Muslim forts in India. Fourth, many technological innovations lead to exploration. The development of the cannon, new sailing and navigational developments, such as the caravel ship, the magnetic compass, and the astrolabe, all supported expansion. They wanted to spread Christianity and their beliefs to foreign countries. People migrated due to limited economic and political opportunity for upperclassmen in Spain. Renaissance curiosity caused people to seek out new worlds. The economic motive, the quest for material profit, was the basic reason for European exploration and expansion.
             The Age of New Imperialism in the 19th and 20th centuries had many motives towards overseas expansion. First, economic motives, especially trade opportunities, were important. Although economic benefits were limited because the new colonies were too poor to buy much. Second, political and diplomatic factors also encouraged overseas expansion. The colonies were believed to be crucial for national security, military power, and international prestige. Many people believed that colonies were necessary to form great nations. The German historian Treitschke claimed that colonies were crucial to show racial superiority and nationa...