"The Emperor has made a critical error and the time for our attack has come. The data brought to us by the Bothan spies pinpoints the exact location of the Emperor's new battle station. We also know that the weapon systems on this Death Star are not yet operational. With the Imperial fleet spread throughout the galaxy in a vain effort to engage us, it is relatively unprotected. But most important of all, we have learned that the Emperor himself is personally overseeing the final stages of the construction of his Death Star. Many Bothans died to bring us this information."
January 1, 1970
https://en.wikiquote.org/wiki/Return_of_the_Jedi