The Emperor's made a critical error, and the time for our attack has come.
The data brought to us by the Bothan spies pin point the exact location of the Emperor's new Battle Station.
We also know that the weapon systems of this Death Star are not yet operational. With the Imperial Army spread through out the galaxy in a vain effort to engage us it is relatively unprotected.
But most importantly of all, we've learnt 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. Admiral Ackbar please