The Hanseatic League was a commercial and defensive alliance of merchant guilds and market towns in Northern Europe that emerged in the late Middle Ages, around the 13th century. It aimed to protect trade interests and ensure safe passage for merchants. The league included cities from modern-day Germany, Poland, Sweden, and the Netherlands, among others. At its height, the Hanseatic League controlled trade routes across the Baltic Sea and North Sea, facilitating the exchange of goods like timber, fish, and grain. The league's influence declined by the 17th century due to changing trade patterns and the rise of nation-states.