Why did Brecht chose the Thirty years war as a setting to the play "Mother Courage and her children"?

Mother Courage and Her Children is set during the Thirty Years' War, but it was written either shortly before or during the early years of the Second World War. Hitler's warmongering intentions had become clear to many Germans by the mid-1930s, and Brecht himself, already opposed to the man he called "the great bandit," had repeatedly emigrated so as to escape the rise of fascism. "The dark times" was how Brecht referred to this era in his writing, and it is against the backdrop of the rise of Hitler that the play was written.