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Wednesday, September 19, 2012

Chess Primer: Calculating Moves

If you have read the other Chess Primer posts on this blog, "Basic Rules" and "Understanding Chess", then you will know how to move the pieces and how to judge (at a very simple level) the effectiveness of a move. In order to play good chess, and follow the games of experienced players, it is also necessary to be aware of several common attacking patterns and combinations, and to be able to calculate if certain moves will lead to an effective attack or a dead end. Chess players refer to a series of moves which require concrete calculation (move by move analysis) as tactics.

Calculating Moves 

Section I: The Double Attack
Section II: The Pin
Section III: Tips on calculating combinations

Section I: The Double Attack

Double attack with a Pawn

Double attack with a Knight

In chess, you can only make one move at a time. Therefore, it stands to reason that if you attack two of your opponents pieces, he can only save one of them. Note that attacking refers not only to capture the enemy piece, but to capture without fear of retribution. This can be thought of as distinct from a trade, in which the capturing piece itself will be taken on the next move (or few moves).

Section II: The Pin

Bishop placing on absolute pin on a Knight

Sometimes a piece cannot or should not move because if it did, a line of attack would be opened against another (usually more valuable) piece. That piece is said to be pinned. Sometimes the pin is absolute: if a piece is blocking an attack on the King, it would be illegal to move that piece (the King must never voluntarily be exposed to attack). Other times, a piece can legally move but is compelled not to because it would lead to the loss of a valuable piece.

The pin is a very common tactic, and is a good way to neutralize the piece you are attacking. If a piece is pinned, especially if it is an absolute pin, then you can regard the squares that piece was controlling as free for your pieces to traverse. Because the pinned piece is immobilized, it also because a great target for attack. Even a lowly pawn can easily conquer a pinned piece!

Section III: Tips on calculating combinations

In the initial position, there are 20 legal moves for White (16 pawn moves, four Knight moves). In response, Black also has 20 legal moves. Quickly, it becomes impossible to calculate all the possibilities, several moves ahead. So how do good chess players play combinations and forsee tactics and ideas three, five, or even ten or more moves in advance?

There are a couple of tips that can help you understand how this is done, and how you can it this yourself. To calculate effectively, you should do two things. First, you should not try to calculate every single move. Some moves are clearly bad, like placing your Queen where it can be captured by a pawn (Not a good trade!). It is often not necessary to consider these moves, or to consider replies by your opponent that do not involve them carrying out the capture of the Queen (in this example). Recognizing these two facts will help you eliminate unnecessary calculations.

Secondly, you should prioritize the way in which you calculate chess moves. In any position, always first consider moves that force your opponent's hand. These include moves that check the King, that capture a piece, or that threaten to capture a piece. As in the previous example, in which a bad move (giving away the Queen) was played, these forcing or compelling moves will mean you will only have to consider and calculate a few replies by your opponent. 

If your move would check the King, then you only need to consider what ways in which your opponent would block or escape from the check/attacking. Calculation of any other moves in that position is unnecessary as they would be illegal moves. If your move captures a piece or threatens to capture a piece, then likely you only need to consider moves from your opponent that attempt retribution for the capture or protect the threatened piece. It is usually not necessary to consider moves from your opponent that ignore your threat (unless their move carries a threat of their own), since if they play such a move, you can simply execute your threat.

Remember, just because you should start with calculating all possible checks, captures, and threats, this doesn't always mean these moves will be good. But ultimately you will save time by analyzing these moves first, and often it is those calculations that will allow you to spot surprising tactics and game winning moves!

1 comment:

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