It depends on the position. Sometimes you can choose a move just on general principles, looking to make sure it doesn’t let your opponent immediately do something to you. At other times, in complicated positions with many threats on both sides, you need to calculate a lot of variations.
In general, there are two components of making good chess moves. *Strategy* is what you are trying to achieve: endanger the opponent’s king, weaken their pawn structure, control a portion of the board, etc. *Tactics* means making sure you can safely carry out that strategy (calculating to make sure you won’t be losing pieces, allowing dangerous counterattacks, etc.).
You might have to think ten moves ahead in an especially complex situation in the opening or middlegame. The only time you would typically have to calculate much further than that is in the endgame, when there are fewer pieces and so the calculations are simpler.
They often do, but it isn’t the only thing. Preparation plays a major part. You need to study most common sequences of opening moves, with all the variations you’re likely to get. You also need to study your opponent’s games to figure out which variations they prefer or not. Most top players have giant files on their computers, with complex decision trees (“If they do this, I’ll do that”), that they try to memorise.
Of course, there are way too many variations to remember. At some point in each game, both players find themselves “out of preparation” and having to figure out what to play on the spot. Generally, based on their prep, they’ll have a good idea of the pros and cons of the position at that point and the general strategic principles at play (“I have a strong centre, but need to watch out for an attack on the kingside”). Also, having played thousands of games over the years, they’ve developed strong pattern recognition that allows them to identify possible tactics.
Therefore, memory and pattern recognition helps them calculate multiple moves in advance. How far in advance depends on how much time they have. In classical games (~90 minutes for 40 moves, with some sort of extension for subsequent moves), it is common to see players thinking for up to half an hour on a critical move, as they explore all the likely variations. However, in rapid or blitz games, you just don’t have the time to do that (luckily, neither does your opponent) so you have to rely on memory, pattern recognition and instincts. The best chess players can think fast and deep, have extraordinary abilities to recall obscure games, and have spent literal decades doing little other than playing and studying chess.
It depends massively on the position. The more available “good” moves and “good responses” exponentially increases the amount of thinking required to think one more move ahead. So in very simple or very forcing(few responses that work) positions high lvl chess players can easily think 10+ moves ahead. But in more complex positions they maybe look 3-5 moves ahead, but spend more time evaluating how good each position is.
Not every move is planned that way. There are some general strategies, such as “control this section of the board”.
I once played a game against my brother, and I was thinking three moves ahead. I was mentally exhausted when it was over, and decided that I didn’t really want to play chess any more. If I’m going to play a game, I don’t want to work that hard at it.
They think 10 moves ahead or more if the line is ‘forcing’. A forcing move is a move which has very few reasonable responses. Like checking the king or capturing a piece. Players will search for forcing lines (sequences of forcing moves). If the line results in some improvement in their position, they will likely go for it, even if they suspect it might not be the best move.
I’d just like to add, if you want to improve at chess and be able to play decently, you can get really far without being able to do those in depth calculation. Just knowing basic principals like control the center, get your king to safety, avoid moving a piece twice in the opening and various tactics like pins and forks will get you decently far with lots of practice. So even if some GMs can make these crazy calculations, don’t think it’s necessary for your average player.
At the beginning of a game high level players learned a set of good moves and good answers by their oponent and the answer to that and so on. That can be 5 moves or 25 moves that they just learned, depending on the strength of the players and the strength of the opening. An opening that is strong will be played more often and it is worth it to memorize more of it.
In the middle game, unless players are forcing specific moves (“If they dont move their queen to this square, I can win with a mate”) it is hard or even impossible to calculate more than 5 moves ahead. Even with some pieces off the board there could be hundreds of ways to make 5 non-idiotic moves each. Then good chess players might take a lot of time, consider different moves, imagine what can happen next, how that would change the game and so on. It helps a lot to have good memory, a lot of games played and remember certain patterns, it makes calculating moves much easier.
In the endgame with less pieces on the board it becomes easier to calculate and therefore the number of precalculated moves can increase again. With very few pieces some endgames are completely solved and pro players might know some of them completely. Especially those that appear often after their prefered openings.
The game can be broken down into three phases really.
The opening. This sets up the game, there are many many well known openings and at a high level it can be who knows the most lines, there are many many responses to openings. This is where the most lines-ahead are. High level chess players will choose to play slightly off main lines to force their opponent to balance their game theory with their book knowledge.
The mid game. As you get further away from the opening the games spin off into more strategy. A lot of pattern recognition and best approach here, typically your opening is trying to force some similar themes in the mid game so you get a lot of similar set ups. This part requires the most game knowledge IMHO.
The end game. As most of the pieces leave the board if the game hasn’t been lost already there’s just end game check mates. It’s a battle of pawn positioning and who can force mates well with few pieces.
All three stages require a different set of skills and are almost 3 games within a game. However the opening sets the tone, certain openings may typically result in gravitating towards a handful of midgame configurations and it’s a matter of how creatively your oponent plays them compared to your previous hundred games with the same opening. For general chess though I would say most advanced chess players can plan out a few lines 7 or so moves ahead but this is also alot of chaining known patterns together.
Pattern recognition.
The human mind is extremely good at it. The average number of legal moves in any legal position is 35. A top player will discard 90% of them out of the bat because they’re just trash. Then they let their brain work their magic on the remaining 10%, using their experience (and sometimes intuition) to figure out which moves look promising. We interpret them as **ideas**. Attacking, defending, positional play, etc.. Chess obviously does not have any real logic embedded in its rules, but it’s how humans approach the game.
Once a top player has settled on a smaller number of moves, they can then **calculate**. That means, they’ll think ahead as many moves as they possibly can using reasonable countermoves they think are best for the opponent, and determine if the position they get is advantageous or not.
A player will not calculate all possible move paths 25 moves deep. Not that it’s impossible at all, it’s pretty much par for the course for a top player to be able to keep track of the position in their head past 10-15 theoretical moves. But they won’t calculate that deep for every single variation. The reason for that is simple: chess is a time-based game. You can spend 40 minutes on a move if you want, but that’s time off your clock. It gives your opponent a time advantage. Also, a player will not calculate until they see a win. That’s just not realistic. They will do so until they can see an advantage or material gain most of the time.
The assertions I’m making here are obviously blanket statements, different players have different thought processes.
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