How does opening preparation work at GM level?

Question

From what I can gather, one studies what the opponent has been playing, and prepare responses for their favourite lines. The problem is, there's no guarantee the opponent will play a given opening. For example, suppose I'm playing against Kramnik with white. Kramnik is the person who famously defeated Kasparov with the Ruy Lopez Berlin, so I prepare something special for 1. e4 e5 2. Nf3 Nc6 3. Bb5 Nf6. But then in the actual game, all I can control is the first move. After 1. e4, it's conceivable that Kramnik plays 1...d5, 1...Nc6, or 1...e6.

My guess would be that GMs have some kind of plan mapped out for every possible response - but that sounds like a formidable amount of lines to remember, especially with opening lines running 15+ moves deep.

Answer 1

Not a GM myself, but my understanding is that there is more than one way.

First of all any decent GM would have notes (nowadays on computer) with all the opening lines they play. These notes might include some new ideas, but would at least give an assessment of the known lines such as "drawish, unclear, big advantage..." Before a game they would consult these notes for the openings their opponent plays. This helps to refresh their memory and also: Depending on the tournament situation and/or the opponent's strength they could select more equal lines or more aggressive ones or perhaps trying out a new.

Another way to prepare for an opponent is to analyze their games and find positions or opening lines your opponent does perform poorly in. For instance if your opponent is not so good at complicated tactics, you would aim for an opening which favors tactics.

Lastly, if it is a major important tournament such as a WC match a player might even prepare a completely new opening repertoire as a surprise weapon.

Answer 2

Professional chess is hard.

• Yes. Professional elite players prepare as many opening lines as they can. They have seconds who are dedicated to opening preparation (generally on a computer). The most well paid players such as Magnus Carlsen has a team of seconds. Read more about chess seconds here.
• The seconds are paid for improving the master's opening preparation. Those guys are generally grandmasters. They would use database, recent trends, common sense etc to make preparation. Some players such as Maxime Vachier-Lagrave are easy to predict. MVL has been a consistent Najdorf players for years.
• Of course, nobody can prepare every single possible response in chess. However, the more a GM prepares the better competitive advantage he has. Chess is a relative game - you don't need to play perfectly, you just need to play better than your opponent.
• No preparation is perfect. All players must sooner or later make a new move. However, the more prepared you are the less likely you're the first player "out of book".
• All professional chess players need to know extraordinary number of possible opening variations. Sometimes they don't remember the exact lines, but they know similar lines or ideas. Then, we would think over the board.
• Most prepared lines are used later on against someone else.

Answer 3

I asked a GM and surmise the following answer. Basically all GMs have an "opening repertoire" which includes every opening. Some of them they'll know especially well, e.g. a player who specializes in the Alekhine's Defense will also know the opening to high depth, but even those who never play the Alekhine's Defense as Black will still know some theory. They won't know as much, but they will know some. In this it is similar to how I, having asked this question previously and internalized the answer, now know the theory of the Giuoco Piano a bit more.

However, not all lines are created equal. There are some lines which are known to be White's best tries for an advantage - e.g. after 1. e4 e5 2. Nf3 Nc6, if White wants to fight for an opening advantage, the "best" try is the Ruy Lopez. Therefore GMs will extensively study the Ruy Lopez. In the same way, the Sicilian and Petroff (and to a lesser extent the French and Caro-Kann) are major openings which anyone playing 1. e4 must be ready to meet.

This does not mean that GMs will always get the opening they want, but the lines they spend less time on are also generally lines which are inferior. Therefore if a GM runs into 1. e4 f5 on the board, they'll be quickly taken out of their opening repertoire, but they should already know enough about the opening to get an advantage. Facing this opening would still be an "opening surprise", but it would be a pleasant one - it is scary to play an unfamiliar position against a prepared opponent, but only if that position isn't in one's favor.

Notably at GM level the line between which openings are good and which are not can be quite surprising to amateurs. For example, it is reasonable to guess that neither Carlsen nor Nepomniatchi, in their World Chess Championship match, have prepared for the King's Gambit, the Bird's Opening, or even the Scandinavian Defense. If the opponent plays it then of course all their seconds will get to work on that opening, but a priori all their efforts are focused on the main openings.

Perhaps surprisingly, if opponent actually plays one of these fringe openings, the reaction is more of joy than dismay. In the example in the OP, a GM preparing to play Kramnik might prepare for the Berlin, but they probably would not find something highly effective. If Kramnik plays 1...Nc6, however, then the GM suddenly gets to play against a known-inferior line, and has a much easier route to an opening advantage.

Edit: as it turns out, even the French Defense is not something to prepare for at world championship level - see Nepomniatchi vs. Ding Liren, World Chess Championship 2023, game 7, where Nepo was clearly caught by surprise on move 1 and avoided the most critical lines as a result. This is even though Nepomniatchi has played the French Defense himself before, most notably the Candidates 2020.