And without a cartaz, a merchant couldn't trade in any of the towns that Portugal controlled. For merchants who'd plied the Indian Ocean trade for years in relative freedom, the Portuguese were just glorified pirates, extracting value from trade without adding to its efficiency or volume. So the cartaz strategy sort of worked for a while, but the Portuguese never really took control of Indian Ocean trade. But they were successful enough that their neighbors, Spain, became interested in their own route to the Indies. And that brings us to Columbus. But first, let's dispel some myths. One, Columbus and his crew knew the Earth was round.