In December 1894, French artillery officer Captain Alfred Dreyfus — a 35-year-old Alsatian of Jewish descent — was wrongfully convicted of treason for allegedly communicating French military secrets to the German Embassy in Paris. The case began in September 1894, when French military intelligence recovered a torn, unsigned note (later called the “bordereau”) addressed to the German military attaché, describing confidential French artillery information. On 5 October 1894, Major du Paty de Clam compared the bordereau's handwriting to Dreyfus's and concluded he was its probable author, despite a dissenting expert opinion finding the writing inconsistent with disguise. Dreyfus was interrogated and arrested on 15 October 1894 after denying the accusation, and was imprisoned at Cherche-Midi prison in Paris. He was tried before a closed military court beginning 19 December 1894; seven judges convicted him unanimously on 22 December 1894, relying on the disputed handwriting comparison and on a secret dossier — containing some falsified documents — illegally submitted to the judges during their deliberations by order of the Minister of War, General Auguste Mercier. On 5 January 1895, Dreyfus was publicly stripped of rank in a degradation ceremony in Paris, then deported to solitary confinement on Devil's Island, French Guiana, arriving on 14 April 1895; he was held there for five years in harsh conditions, including extreme heat and inadequate food and medical care. On 6 September 1896, following a false report by a British newspaper that he had escaped, his guards began shackling him nightly for two months.
In March 1896, Lieutenant Colonel Georges Picquart, the army's newly appointed counter-espionage chief, intercepted an unsent telegram implicating a different officer, Major Ferdinand Walsin Esterhazy, in contact with the German military attaché, and found that Esterhazy's handwriting matched the bordereau used to convict Dreyfus. After reviewing the secret file used against Dreyfus, Picquart became convinced of his innocence; when he raised his findings, army leadership suppressed them and transferred him to Tunisia. On 1 November 1896, a deputy head of the army's Statistics Section fabricated a supporting document that was brought to the Minister of War, General Jean-Baptiste Billot, as genuine evidence against Dreyfus. Independently, Dreyfus's brother Mathieu traced the bordereau's handwriting to Esterhazy and, on 15 November 1897, filed a formal complaint against him, forcing the army to open an inquiry; ten days later, novelist Émile Zola published the first of three newspaper articles in Le Figaro taking up Dreyfus's cause. A military court nonetheless acquitted Esterhazy, and the army brought further charges against Dreyfus based on additional forged documents. Zola's subsequent open letter, “J'Accuse…!,” published in the newspaper L'Aurore, further mobilized public support for Dreyfus and divided French society into pro-Dreyfus “Dreyfusards” and opposing factions.
In 1899, Dreyfus was returned to France for a second court-martial, which again convicted him and imposed a ten-year sentence; he was pardoned and released shortly afterward. In 1906, Dreyfus was formally exonerated. He was reinstated as a major in the French Army, served throughout World War I, was promoted to lieutenant colonel, and died in 1935. The affair came to symbolize modern injustice in the Francophone world and remains one of the most notable examples of a miscarriage of justice and antisemitism in French history.