I've just read a question about Luke Skywalker learning Form IV from Yoda. This would have had to happen before Yoda died (maybe).
I don't remember lightsaber combat forms being mentioned in the films, so it must have been added retroactively to the canon, right? Except I know midichlorians were thought of by George Lucus long before they were mentioned in the prequel trilogy.
When did the idea that lightsaber combat had forms first occur?