Originally posted by: zombie84
Around 1975 or 1976, he wrote down the character histories that exist mentally in every writers head. This resulted in a note collection of about "8 or 9 pages", in his words, which contained character sketches and background details, such as the formation of the empire and fall of the republic, the nature of the jedi, the broad history of people like obi wan and palpatine. Some of this found its way into the prologue of the novelisation in 1976, which, if you read, gives a pretty approximate parallel to the political-based plot of the PT.
So, in a sense, yes he sorta did, but in a larger sense, not really. He didn't plan it to be a series or ever shown on film, and it was vague and nothing special, the same background development that stems from any reasonably-complex story, and many of the pivotal prequel details (ie Darth Sidious, Anakin becoming Vader, Yoda, etc.) were absent and not added until ESB and ROTJ era.
That's what's neat about the sequels. As the story progresses you find out more of the backstory. This even continued into the Timothy Zahn novels, although I haven't gotten around to reading all of the thrawn trilogy yet. It's cool that they kept coming back to him for novels even during the prequel era, because not only does that solidify his first SW novels as canon, it brings them even more to the forefront. That's the gift and the curse of the EU. It's not that it "didn't happen" if something like Darth Maul's Exar Kun saber shows up in one of Lucas's movies. It's just that it's suddenly not as important because the movies are the movies and the books are the books, at least that's how one of my older friends put it. 
