Captain Alfred Dreyfus was a French-Jewish artillery officer in the French army. In September 1894 French intelligence found information about someone giving the German Embassy military secrets. Anti-semitism seems to have caused senior officers to suspect Dreyfus, though there was no direct evidence of any wrongdoing. Dreyfus was court-martialled, convicted of treason and sent to Devil's Island in French Guiana.
Lt. Col. Georges Picquart came across evidence that implicated another officer, Ferdinand Walsin Esterhazy, and informed his superiors. Rather than move to clear Dreyfus, the decision was made to protect Esterhazy and ensure the original verdict was not overturned. Major Hubert-Joseph Henry forged documents that made it seem that Dreyfus was guilty and then had Picquart assigned to duty in Africa. Before leaving, Picquart told some of Dreyfus's supporters what he knew. Soon Senator August Scheurer-Kestner took up the case and announced in the Senate that Dreyfus was innocent and accused Esterhazy. The government refused new evidence to be allowed and Esterhazy was tried and acquitted. Picquart was then sentenced to 60 days in prison.
Zola risked his career and more on 13 January 1898, when his "J'accuse" was published on the front page of the Paris daily L'Aurore. The newspaper was run by Ernest Vaughan and Georges Clemenceau, who decided that the controversial story would be in the form of an open letter to the President, Félix Faure. Zola's "J'Accuse" accused the highest levels of the French Army of obstruction of justice and antisemitism by having wrongfully convicted Alfred Dreyfus to life imprisonment on Devil's Island. Zola's intention was that he be prosecuted for libel so that the new evidence in support of Dreyfus would be made public. The case, known as the Dreyfus affair, divided France deeply between the reactionary army and Catholic church and the more liberal commercial society. The ramifications continued for many years; on the 100th anniversary of Zola's article, France's Roman Catholic daily paper, La Croix, apologized for its antisemitic editorials during the Dreyfus Affair. As Zola was a leading French thinker and public figure, his letter formed a major turning-point in the affair.
Zola was brought to trial for criminal libel on 7 February 1898 and was convicted on 23 February and removed from the Legion of Honor. Rather than go to jail, Zola fled to England. Without even having had the time to pack a few clothes, he arrived at Victoria Station on 19 July. After his brief and unhappy residence in London, living at Upper Norwood from October 1898 to June 1899, he was allowed to return to France in time to see the government fall.
The government offered Dreyfus a choice between a pardon (rather than exoneration), which would allow him to go free (provided that he admit to being guilty), or facing a re-trial in which he was sure to be convicted again. Although he was clearly not guilty, he chose to accept the pardon. Zola said of the affair, "The truth is on the march, and nothing shall stop it." In 1906, Dreyfus was completely exonerated by the Supreme Court.
The 1898 article by Zola is widely marked in France as the most prominent manifestation of the new power of the intellectuals (writers, artists, academicians) in shaping public opinion, the media and the state.