By 1820, N M Rothschild & Sons bank was already operating successfully in London, England, de Rothschild Frères in Paris, and S M von Rothschild in Vienna, Austria where Salomon Mayer von Rothschild became a powerful ally of Austria's Prince Klemens Metternich. In March 1821, in support of King Ferdinand I of the Two Sicilies, the Austrian army entered the Sicilian Kingdom and occupied Naples. This event opened the door to the Rothschild interests and Carl von Rothschild was sent to Naples where he established C M de Rothschild & Figli to operate as a satellite office to the Rothschild banking family of Germany headquarters in Frankfurt am Main.