Bernard Lazare's consistent efforts began to pay off in other ways: he had posters put up in the streets, showing side by side the bordereau and Dreyfus' letters. A banker named Castro recognized the handwriting of his client - Esterhazy - and informed Mathieu Dreyfus. Taken together with the conclusions of Scheurer Kestner, it was a sign Esterhazy's time had run out. In a letter to War Minister, General Billot, dated November 15, Mathieu denounced Esterhazy. General Pellieux was put in charge of the investigation.

The right-wing press immediately opened fire. An article in La Libre Parole, probably written by Henry, showered abuse on Picquart, accusing him of being the linchpin of the plot against Esterhazy. Le Figaro published letters by Esterhazy, in which the count showed himself in a markedly unpatriotic light. General de Pellieux concluded his report by sending Esterhazy for court-martial. But he also asked for a Commission of Enquiry into Picquart's fitness for service. Amazingly, Esterhazy was acquitted in three minutes, without any dissenting opinions among the judges. Picquart was confined to the Mont-Valerien Fortress. Scheurer-Kestner was not re-elected Senate Vice-President. The press had more impact on the government more than on public opinion. The first attempt to reopen the case had failed, lacking press support, while the right-wing press had demonstrated its power in protecting Esterhazy. Neither the authorities nor the parliament had been willing to take the issue up again, against such formidable opposition.

The answer had to lie with a single individual. Writer Emile Zola, who had for several years been sickened by the nationalist and anti-Semitic campaigns and had early on concluded that Dreyfus was innocent, became involved in the campaign through an open letter that he wrote to the President of the Republic.

Zola decided to use the powerful press as his instrument to carry out what has been termed the greatest revolutionary act of the century. In a few hours, over 200,000 copies were sold of Zola's article "J'accuse" (I accuse), published in L'Aurore on January 13, 1898. It has been called the "greatest day" of the entire Affair, and at a point when hopes were at their lowest ebb, it certainly injected strength and confidence into the pro-Dreyfus camp. Zola had dealt a decisive blow in the battle for public opinion, cutting through political interventions and silent petitions to bring the debate out into the open. In under a month, he transformed the Dreyfus Affair into a public issue. The authorities had no choice but to defend themselves.

Under parliamentary pressure, the President of the Council agreed to institute legal proceedings for libel against Zola. The real battle was about to begin. Dreyfus, whom Zola had turned into a myth, remained the centre of the struggle. Those in the pro-Dreyfus camp were amazed at the scale of developments. Since he was to appear before a civil court, Zola thought that he would be able to confront public opinion directly with the Affair, and have it evaluated in the full glare of publicity, without any in camera proceedings, as if he was appearing in Dreyfus's stead.

From this critical moment on, the Affair proceeded along two parallel tracks. On the one hand, the State threw all its repressive forces into trying to shrink the Zola trial to an ordinary libel case and to prevent the Zola case from being tied up with the Dreyfus case, which had already been decided; and on the other hand, the battle for public opinion tried, outside official settings, to force the hand of either the government or Zola's judges in order to have the Dreyfus case reconsidered or the author of J'accuse himself found guilty as charged. Maximum sentence was passed on Zola: a stiff fine and one year in prison (in actual fact, he served one month and left for England).