Mercantilism taught that trade was a zero-sum game, with one country's gain equivalent to a loss sustained by the trading partner. Overall, however, mercantilist policies had a positive impact on Britain, helping to transform the nation into the world's dominant trading power and a global hegemon. One domestic policy that had a lasting impact was the conversion of "wastelands" to agricultural use. Mercantilists believed that to maximize a nation's power, all land and resources had to be used to their highest and best use, and this era thus saw projects like the draining of The Fens.