Esterhazy, Ferdinand Walsin, 1847-1923, French army officer, member of a French family possibly related to the Hungarian family of Esterhazy. A veteran of the papal army and the French Foreign Legion, he entered the regular French army and rose to be a major. Deep in debt, he sold French military secrets to the Germans. When treason became evident in 1894, the guilt was pinned on Captain Dreyfus (see Dreyfus Affair). The suspicions of Col. Georges Picquart helped to bring about a court-martial for Esterhazy in 1898, but his fellow officers quickly acquitted him. He subsequently fled to England, where he later confessed.