In 1900, Walter succeeded Schalk at the Berlin State Opera and made his first recordings, beginning a career that would stretch into the era of stereo and number in the hundreds of titles. He also conducted his first orchestral concert, the featured work being Berlioz's Symphonie fantastique. In 1901, Walter decided he was ready to take advantage of Mahler's open invitation to join the Vienna Court Opera as an assistant. Walter stayed in Vienna until 1913, taking Austrian citizenship in 1911. After Mahler died, Walter mounted the premieres of Das Lied von der Erde (Munich, 1911) and the Mahler Ninth (Vienna, 1912). In 1913, Walter moved to Munich to lead the Bavarian Court Opera, and this is where his conducting career took wing. He revived the long-neglected Mozart operas, attracted worldwide attention for his careful handling of operas by Wagner and Verdi, and premiered significant new operas by Korngold and Pfitzner. Walter abruptly left Munich in 1923, embarking upon a variety of destinations, including the United States, Great Britain, Paris, Rome, and the U.S.S.R. In 1925, he helped institute the Salzburg Festival and was named musical director of the Berlin Municipal Opera. In 1929, Walter had a falling out with the Berlin management, and departed to succeed Wilhelm Furtwängler at the Leipzig Gewandhaus. When the National Socialists came to power under Hitler in 1933, Bruno Walter was stripped of his post in Leipzig and took refuge in Vienna. He was a guest conductor with the Vienna State Opera and was named musical director of the Vienna Philharmonic in 1935; during this time he also frequently appeared with the Amsterdam Concertgebouw. When the Nazis took Austria without firing a shot in 1938, Walter was on the run again, this time to France and the Paris Conservatoire. His stay in France proved brief, as in 1939 Walter escaped to the United States. Walter settled in Los Angeles and remained based out of Southern California for the rest of his long life. While Walter's American period is most readily associated with the New York Philharmonic, he conducted a number of American orchestras in these years, especially the Los Angeles Philharmonic, but also the Minneapolis Symphony, the NBC Symphony, and at the Metropolitan Opera. After the war, Walter made a number of return visits to Vienna and other European cities, and in London recorded Mahler's lieder with Kathleen Ferrier, his own favorites among his recordings. A heart attack in 1957 caused Walter to curtail his engagements, and he made his official farewell appearance in Vienna in 1960 conducting Mahler's Fourth, although his true final engagement was with the Los Angeles Philharmonic in an all-Brahms program given December 4, 1960.
Walter's catalog of original works contains two symphonies, choral works, and a violin sonata; however, all of his endeavors as a composer were completed before 1911.