Mahatma Gandhi’s letter to Adolf Hitler in 1939 asking him to avoid war. The British government, which governed India at the time, intercepted the letter, and it is believed that Hitler never actually read it. The letter was not widely publicized at the time and only gained wider attention in subsequent years, becoming the subject of analysis and debate among historians.
This wasn’t the only time Gandhi tried to reach out to leaders involved in conflicts. He also corresponded with British leaders and others but Hitler was arguably the most controversial addressee.