Hey guys. I was just wondering what you guys thought it meant to master a particular chess opening or opening system? Does it mean to be familiar with thousands of variations? Or does it mean you win every time you play that particular opening? Maybe it means you can play a 25 move variation from memory fairly well in master play? Just wondering what your thoughts are. Thanks.

To me, it means your able to make the correct move when your opponent deviates from standard, published lines.

I don't necessarily think it means the memorization of thousands of variations, although strong theoretical knowledge would seem to be a given if one claims to have "mastered" an opening variation. Mostly, I believe having mastered an opening line is to know how to play the main lines, take advantage when your opponent plays "lesser" (dubious) moves, have a deep understanding of middlegame tactics and positional ideas, and a solid understanding of the arising pawn structures and how they affect the course of the game and future endgame ideas.

I would assume that to have such knowledge, which clearly goes far beyond the everyday individual's understanding, one would also score very well against most of his opposition. Afterall, though it might be your favorite line, if you're getting slaughtered in it every game you are probably doing something wrong, and therefore haven't truly mastered the proper ideas. Truly, a mastery of something would be to have a solid all around ability for it.

To know the strategies associated with the most common piece and pawn formations.

Thanks for the responses guys. That helps a lot.

To me, mastering an opening means:

 - Understanding the ideas behind the moves

 - Understanding what kind of positions arise out of the opening

 - Understanding what kind of middlegame plans follow

Of course mastering an opening does not guarantee anything other than perhaps getting a decent game out of the opening. I have played games against good players that knew openings and have gotten lost games quickly even though my moves seemed sensible and followed sound general opening principals. This usually happens in sharp openings where every move is important and where tactics trump positional play.

In addition to the things posted by salimb, I would say the main thing to know that you've mastered the opening is how you respond to moves that aren't book but are sill playable.

When you can do that effectively, the opening is mastered. Complete mastery of an opening would mean you are aware of the following middlegames. If you knew all the middle- and end-games that could arise then you would beat players hundreds of points above your rating using that opening.