The appearance of Portuguese explorers in India in 1498 was, it’s safe to say, a world-altering event. When Vasco da Gama proved that it was possible for European ocean-going vessels to reach India by going around Africa, it meant changes not only for Europe and India, but for the kingdoms in between, whose economies had depended to one extent or another on extracting rents from commercial traffic along the various Europe-to-India routes. Here I’m talking about a number of Muslim states—the Ottomans, the Mamluks, the various dynasties that controlled northern India and Iran. But I’m also talking about Christian Venice, which made a lot of bank ferrying eastern luxuries across the Mediterranean Sea to European customers.
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I always thought it was the combination of the two. The Ottoman conquest got people thinking about alternative routes to the East, and the fact that the Portuguese had claimed the around-Africa route for themselves motivated Spain to try a different direction. At the time, some people actually thought the western route would be shorter than going around Africa, but the Portuguese weren’t buying it.