The Thule Society was a German group in that operated during and after World War I. Based in Munich, the Society was named for Thule, the mythical northern city of Ancient Greek legend. Many Thule Society members, including Dietrich Eckart, the basis for the character Dietlinde Eckhart, were supporters of Adolf Hitler. The Thule society created and sponsored the German Workers' Party which would later be transformed by Hitler into the National Socialist German Workers' Party (the Nazi Party). The Thule Society was dissolved around 1925.
In Fullmetal Alchemist
During the events of Conqueror of Shamballa, the Thule Society was run by Dietlinde Eckhart. The goal of the Society was to return power to Germany following its defeat in World War I and weakening by the Treaty of Versailles. Eckhart planned to do this by taking control of the mythical kingdom "Shamballa", later discovered to be the alchemical universe. By capturing the serpentine Envy, the Thule Society was able to pass members multiple times through the Gate to the alchemical world, including armored soldiers and Eckhart herself. In order to pass through the Gate, the Society enlisted the help of Alfons Heiderich and his colleagues to build a rocket that would give them enough kinetic energy be able to enter the other world. Once inside the alchemical universe, Eckhart proceeded to attack Central City in an effort to conquer it and the rest of the world and present it to Hitler. The Amestrians were devastated by Eckhart's war machine and her newfound alchemical prowess until she was stopped by the State Military along with Edward and Alphonse Elric and Roy Mustang.