text: Three brothers who ruled this polity had the awesome nicknames "Achilles," "Irontooth," and "the Alchemist.
full_question: Three brothers who ruled this polity had the awesome nicknames "Achilles," "Irontooth," and "the Alchemist." The Treaty of Eltville ended a civil war in this polity that pitted the pretender "False Waldemar" against Louis I of the Wittelsbach dynasty. This polity's founder won a succession war after the death of the Hevelli prince Pribislav-Henry and made a red eagle its heraldic symbol. That member of the House of Ascania created this polity out of the Northern March and was named Albert the Bear. This polity gained control of Ravensberg and Cleves-Mark in the Treaty of Xanten under a ruler whose daughter Maria Eleonora married Gustavus Adolphus. That margrave of this polity, John Sigismund, was the grandfather of Frederick William the Great Elector. 10 points, name this polity in present-day northeastern Germany that formed a personal union with the Duchy of Prussia during the 17th century.
first_sentence: Three brothers who ruled this polity had the awesome nicknames "Achilles," "Irontooth," and "the Alchemist.
raw_answer: Electorate of Brandenburg [or March of Brandenburg; or Margraviate of Brandenburg; or Brandenburg-Prussia; do NOT accept or prompt on "Prussia" or "Province of Brandenburg"]