Dreyfus Affair
When he was in prison, people (mostly his brother Mathieu and a high-ranking officer called Picquart) thought he was innocent. They proved that another soldier, Major Esterhazy, was guilty. But the army did not want to admit that it had been wrong.  They refused to free him.  Finally, the evidence that Dreyfus was innocent became so strong that the government had to demand a new trial.  At the new trial, the army again found him guilty.  The President of France, who did not want an innocent man to suffer any more, pardoned Dreyfus in 1899.