Mercantilism was an economic doctrine prominent in Europe between the 16th-18th centuries that advocated for government control over foreign trade to ensure national prosperity and security. It promoted a positive trade balance and led to colonial expansion and frequent wars between European powers competing for resources and trade advantages. While criticized by Adam Smith and others, mercantilist policies influenced European economic thought and imperialism until the 19th century. The document also discusses different types of modern barter systems as an alternative form of exchange.