In 1945, secret emissaries offered him the co-directorship of the Metropolitan Orchestra of Budapest (later Budapest Philharmonic Orchestra); he also became principal conductor of the Budapest Opera. He conducted opera at the Vienna Volksoper and at the Salzburg Festival in the late 1940s, including world premieres in Salzburg of operas by Gottfried von Einem ("Danton's Tod" in 1947) and by Frank Martin ("Zaubertrank" in 1948). The enthusiastic reception of Fricsay's work on this international stage led to his being appointed Chief Conductor of the Berlin RIAS Symphony Orchestra and General Music Director of the Deutsche Oper Berlin, from 1949–1952, performing then in the Theater des Westens. He made his United Kingdom debut at the 1950 Edinburgh Festival, leading the Glyndebourne Opera in Mozart's Le Nozze di Figaro. He made his Buenos Aires debut that year with Carmina Burana. In 1951 he made his debuts in Italy and with the Royal Concertgebouw Orchestra in Amsterdam. In 1953 he made his debuts in Paris, Milan, Lucerne, and the US, where he conducted the Boston Symphony Orchestra and San Francisco Symphony. He was appointed musical director of the Houston Symphony in 1954, but resigned halfway through the season over "disagreements on musical policy." The true reason involved US tax policy. He discovered that under the Internal Revenue Code he would have to declare income earned throughout the world in his US tax return as long as he spent more than 6 months residing in the United States. His contract with the Houston Symphony would have resulted in having his income becoming subject to prohibitive US tax rates. When he became aware of this problem he abruptly left Houston for Switzerland. He made his debut with the Israel Philharmonic in 1954. He spent much of his time from the 1950s onward in Germany as music director of the Bavarian State Opera (1956–1958) and as conductor of the RIAS Symphony Orchestra, the Deutsche Oper Berlin and the Berlin Philharmonic. Also in 1956, he was appointed General Music Director of the Munich Court Opera, a position he held until 1958.