Sixtus of Bourbon-Parma, Prince, 1886–1934, son of Robert, last duke of Parma. While serving as an officer in the Belgian army, he was the intermediary for his brother-in-law, Emperor Charles I of Austria-Hungary, in Charles's secret attempt to negotiate peace with the Allies in 1917. The effort came to nothing, but in Apr., 1918, the French government, in retaliation for attacks made by the Austrian foreign minister Czernin, published a letter written by Charles to Sixtus. The letter justified French claims to Alsace-Lorraine, and its publication caused acute embarrassment to the Austrian government.
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