Some three years after Dreyfus had been arrested, his brother and the small group of Dreyfusards launched what they hoped would be the final campaign for revision of the case of the
. ‘Mr Minister’, Mathieu wrote to Billot in an open letter of 16 November 1897,
The only basis for the accusation against my unfortunate brother in 1894 was an unsigned, undated letter stating that confidential military documents had been given to a foreign power. I have the honour of informing you that the author of that letter is Count Walsin-Esterhazy, Infantry Commandant… I cannot doubt that knowing the author of the treason for which my brother was condemned you will quickly have justice done.