**What stages of revisions were done to the original Star Wars trilogy? meaning, how many times were they changed, when, and why?**

It seems there was [one for the recent Blu-ray release][1]. I know the Young Anakin ghost was added to Return of the Jedi.

What I am most curious about is in *A New Hope* and *The Empire Strikes Back*. We're watching the whole set in preparation for *The Force Awakens*. Parts of the light saber battles look enhanced compared to other parts of the same battles, and parts of the space flight and/or fight scenes have the same effect. **Did those scenes actually get changed to be more action-packed and cool?**


  [1]: https://movies.stackexchange.com/q/54/20379