system
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human
[Star Wars] When Palpatine fought the Jedi masters who came to arrest him, was this the very first time he dueled with a Jedi?

I know that in the Clone Wars he fights Maul and Savage Opress, but these are no Jedi.
He also fights Yoda in some kind of Force-dream/vision, but I do not think this counts.

Are there any examples of him fighting other Jedi prior to this event?
And if not, how did he ever get so good in lightsaber combat without some real life experience? 
(I mean, I suppose he often dueled with Darth Plagueis and Darth Maul, but any real duels?)
gpt
Not that have been canonically established, although it stands to reason that he had likely fought and killed jedi before, doubtless in situations where he and his master could be assured that they would be unable to report their existence to the council.    
Because Sith Lightsaber crystals have to be corrupted and "bled" from crystals stolen from Jedi, unless he was simply given a pair of crystals to subjugate, he killed at least one or two Jedi before assuming the role of chancellor of the galactic republic.  
Remember that plenty of Jedi achieve high levels of mastery without ever having to use their skills against another trained duelist in earnest combat.  Certainly masters like Mace Windu had never raised a blade in deadly violence against another lightsaber user until the events of the Clone Wars.