In January 1866, Emperor Napoleon III, influenced by French public hostility to the Mexican expedition, decided to begin the withdrawal of his troops supporting the Imperial cause in Mexico. This strategic pullback was a potentially fatal blow to the infant Mexican monarchy; at the end of the withdrawal of the French expeditionary force, Maximilian would only have the support of a small force of imperial Mexican soldiers and a contingent of Belgian and Austrian volunteers, which were easily outnumbered by rebel forces. The announcement of the French withdrawal encouraged the Belgian legation to leave the country. In a desperate attempt to save her husband's throne, Charlotte resolved to personally persuade Napoleon III to reconsider his decision. On 9 July 1866, Charlotte set sail for Europe from the port of Veracruz upon the transatlantic ocean liner "Impératrice Eugénie". She was accompanied by Martín del Castillo y Cos, Minister of Foreign Affairs, and her two adoptive sons, the Princes of Iturbide.