It happened on the treason conviction which took place in 1894 of Alfred Dreyfus, a artillery officer in the French army with Jewish origin, or as the public knows it "The Dreyfus affair". Dreyfus was accused with passing military secrets to the German Embassy in France. In fact, he was innocent. The whole conviction was based on false, supposedly incriminating documents. Dreyfus was sentenced to a life time of imprisonment.
Secrets started leaking. It was actually a big cover up operation, which featured forgery and perjury against their own country. The conspirators were at least eight generals, assisting Major Marie-Charles-Ferdinand Esterhazy, the one that actually have committed the crime, for which Dreyfus took the blame. That was established by Colonel Picquart the new chief of the French intelligence service. The army refused to reopen the case and Picquart received a posting to Tunisia. His successor began to manufacture evidence to prove Dreyfus's guilt, but meanwhile so many questions had been raised in public that a trial of Esterházy became inevitable.
At this point comes Emile Zola. A famous French novelist, who exposed the affair to the general public in the Paris newspaper "L'Aurore". It was an article written in the form of an open letter to the President of France in 1898, where he attacked the army's actions against Dreyfus in an the title "J'accuse" ( I accuse ). There he accuses the army, of the cover up and shows Esterhazy as clearly guilty and Dreyfus as unjustly punished.
"As they have dared, so shall I...