Since 1592, Sigismund negotiated marriage between Anna and Margrave John George of Brandenburg but political tensions kept delaying the agreement. In February 1598, Sigismund demanded that Charles allowed Anna to return to Poland as her wedding to John George was finally set to Easter that year. Charles attempted to prevent her departure by demanding an inventory of her Swedish property and the promise that it would be confiscated by the state should she die unmarried. Anna protested, advised Charles to cooperate with Sigismund and offered herself as a mediator. At the return of Sigismund to Sweden, Anna immediately joined him in the civil war that erupted between Sigismund and Charles. She was given the task to mediate, but because of Charles' lack of confidence in her, she was not able to achieve much. After Sigismund's defeat at the Battle of Stångebro in 1598, she left Sweden to live with him in Poland.