Before revision: This was a major step in the history of navigation, when an understanding of winds in the age of sail was crucial to success: the European sea empires would never have been established had the Europeans not figured out how the trade winds worked.
After revision: This was a major step in the history of navigation, when an understanding of winds in the age of sail was crucial to success: the European sea empires would never have been established had the portuguese not figured out how the trade winds worked.