In 1914 Ebert was called up for military service, but after a year he was released at the instigation of the Schauspielhaus, Frankfurt, which was in urgent need of a leading actor. In the next seven years he played major roles for the Frankfurt company, and in 1919 he co-founded the Frankfurt Drama College. In 1923 he and his wife divorced. The following year she married the conductor Hans Oppenheim (later a colleague of Ebert at Glyndebourne), and Ebert married Gertrude Eck. All four remained on close terms with one another. Ebert's second marriage lasted for the rest of his life; he and Gertrude had two daughters and one son. Carl's grandson is Alex Ebert. In 1922 Ebert returned to his native Berlin, where he joined the Berlin State Drama Theatre, continuing to build a reputation as one of Germany's leading actors. His greatest success was in the role of Leicester in Schiller's "Mary Stuart". While continuing to act with the Berlin company he was appointed director and professor at the new State drama school at the Hochschule für Musik in Berlin, a post he held for two years. In 1927 he was appointed Generalintendant of the Landestheater Darmstadt, the first actor to hold the post. There he directed his first opera productions, "Le nozze di Figaro" and "Otello" (1929). For the next four years he refined his ideas for modernising the production of opera. In 1931 he was appointed to run the Städtische Oper in Berlin. Among the productions during his tenure were the world premiere of Weill's "Die Bürgschaft" in 1932, and a new production of Verdi's "Un ballo in maschera" in the same year, on which he collaborated for the first time with the conductor Fritz Busch. When the Nazis came to power in 1933, Hermann Göring, in his capacity as chief minister of Prussia, offered Ebert an expanded role, with control of all the opera houses of Berlin. Ebert, politically hostile to Nazism, preferred instead to leave the country and base himself and his family in Switzerland, where he rented a home in Lugano. He directed at the Schauspielhaus Zürich, the Maggio Musicale Fiorentino in Florence and the German opera season at the Teatro Colón in Buenos Aires. During four seasons at the Colón Ebert worked closely with Fritz Busch, who, like him, was a voluntary exile from Nazi Germany.