Loy Hays - Winning Chess Tactics for Juniors, 1991 As the name implies, the double attack is a simultaneous attack on two enemy pieces. Every piece can potentially double attack enemy units, even the lowly pawn is often involved. Very impressive is the long range striking power of the queen in double attack situations, although the rook and (more rarely) the bishop can offer fine examples.
Istvan Pongo - Tactical Targets in Chess, 1986 A tactical blow is called double attack when a piece or a pawn can attack two or more pieces of the opponent.
Arthur Yusupov - Build Up Your Chess 1: The Fundamentals, 2008 An attack on two or more pieces with a single move is called a double attack. The most common form of double attack is the fork, but there is also the skewer, where the two attacked pieces lie on the same line, and the second piece is attacked 'through' the first one. A double attack is a very important and effective tactic. It often leads to an immediate win of material, because the opponent is not able to fend off several threats simultaneously. It is also very easy to overlook a double attack. Every chess piece (though it is most often the queen or the knight) can carry out a double attack.
David MacEnulty - The Chess Kid's Book of Tactics, 2003 A fork in chess occurs when one unit attacks two or more enemy units. A fork is sometimes referred to as a double attack, although the term double attack can also have much broader meaning. All the pieces can fork, but the queen and knight, attacking in eight different directions, are the best pieces to fork enemy units.
Arthur Yusupov - Build Up Your Chess 1: The Fundamentals, 2008 To protect yourself against double attacks by your opponent, you must try not leave any of your pieces unprotected. And opposing pieces which have no defenders are possible targets for our double attacks. A double attack is particularly effective if one of the pieces under attack is the king.
Arthur Yusupov - Build Up Your Chess 1: The Fundamentals, 2008 If, by moving away, a piece opens up a line of attack(file, rank or diagonal) for a piece lying behind it, this is called a discovered attack. A discovered attack is particularly effective if it is linked to a threat of mate, or if a very valuable piece is attacked. David MacEnulty - The Chess Kid's Book of Tactics, 2003 A discovery is like the pin and skewer, except that instead of an enemy unit between you long-range attacker and the enemy target, your own piece is blocking the attack. In a discovery, you move your blocking piece out of the way, revealing an attack from the long-range piece behind it. Naturally, you would like to do as much damage as possible with the moving piece. If you can attack something else with the moving piece, then you have two attacks at once. Frequently, your opponent will have to give up something.
Arthur Yusupov - Build Up Your Chess 1: The Fundamentals, 2008 A particularly effective form of this attack is the discovered attack with check. The piece which moves away frequently wins material on the next move, because the opponent must first react to the check.
Arthur Yusupov - Build Up Your Chess 1: The Fundamentals, 2008 Double check is a simultaneous attack, in which two pieces check the opposing king. This form of double attack can only be achieved via adiscovered check. A double check is particularly dangerous for your opponent: the only move he can make is a king move. A mate by double check is also easily overlooked.
Yakov Neishtadt - Test Your Tactical Ability, 1984 The pin is nearly the most widespread tactical device. What happens in a pin is that a piece (or a pawn) en prise from the queen, rook, or bishop is totally or partially deprived of movement, as it is shielding another more important or undefended piece positioned on the same line. If the pinned piece is shielding the king, its mobility is limited to the utmost - the only movement possible is along the line of attack. Loy Hays - Winning Chess Tactics for Juniors, 1991 Pinning is one of the most frequently occurring tactical motifs. The pin involves an attack on an enemy piece which is situated on a straight line (file, rank, diagonal) and in front of a more valuable piece. Since the first piece "in line" is pinned down and, reluctantly, subject to capture. There are two kinds of pins, the absolute and the relative. An absolute pin involves a piece in front of its king, which cannot legally move away to protect itself since this would leave the king in check. For this reason the absolute pin is normally very damaging.
Arthur Yusupov - Build Up Your Chess 1: The Fundamentals, 2008 The pin can often bring about a tactical or a positional advantage. For that reason, you must fight against any pin with due urgency, or even prevent one occurring. The pin is not only a tactical motif, but is also an important positional device.
Loy Hays - Winning Chess Tactics for Juniors, 1991 The relative pin is one without the king's involvement. In some of these cases the pinned piece may be able to move away if it can in turn produce a stronger threat of its own. For this reason relative pins must be examined with some degree of caution.
David MacEnulty - The Chess Kid's Book of Tactics, 2003 A skewer is like a pin, except that instead of attacking a weaker piece in front of a more important one, the more important piece is in front. When the more important piece moves away to escape the attack, the piece behind it can be taken. If the pieces under attack are of equal value, say two knights, that is also a skewer.
Yakov Neishtadt - Test Your Tactical Ability, 1984 As a tactical device the decoy is used with the aim of removing a guard. When the guard is destroyed this removal is accomplished directly - by the straightforward capture of the piece (or the pawn) fulfilling an important function. From the aesthetic point of view, combinations involving the guard are less striking, because they inevitably include a capture.
Istvan Pongo - Tactical Targets in Chess, 1986 Removing a piece from a given square or from the defence of it.
David MacEnulty - The Chess Kid's Book of Tactics, 2003 In a deflection you chase a piece away from an important defensive post. You can do this by either attacking it to make it move away, or by forcing it to take one of your pieces. In accepting your sacrifice, a piece will have been deflected away from its original position, and you can take advantage of its absence. Some writers call this idea distraction or driving away.
Loy Hays - Winning Chess Tactics for Juniors, 1991 This device is usually employed to attract an enemy piece onto an unfordable square. Sometimes this implies that the piece being so attracted is placed under attack. The actual attraction is usually accomplished by a forcing sacrifice. Often a sacrifice will attract the king, exposing it to attack. The attraction motif occurs quite frequently and careful analysis is suggested.
Istvan Pongo - Tactical Targets in Chess, 1986 Forcing a piece to move to a given square.
Yakov Neishtadt - Test Your Tactical Ability, 1984 Tactical device that forces the opponent's piece or pawn to leave its position and give access to an important square or line. The motives behind the operation (or its final aims) can vary.
David MacEnulty - The Chess Kid's Book of Tactics, 2003 Sometimes you want an enemy piece to move to a new square so you can do something to it in its new location. The technique we use for this is called the decoy. Other terms for the same idea are driving on, attraction and luring. Some authorities use the term decoy only as an endgame term, where one side has an outpost passed pawn that is sacrificed to lure the opposing king away from the main body of pawns on the other side of the board. However, maxim Blokh and Yasser Seirawan, in their excellent book on tactics (The Art of Combination, 1997), use the term as it is used here.
Yakov Neishtadt - Test Your Tactical Ability, 1984 Line Closing : with this tactical device the connections between the opponent's pieces positioned on one line can be broken, or access to a key square can be denied.
Yakov Neishtadt - Improve Your Chess Tactics, 2011 In combinations using the theme of Interference or Shutting-Off, we either see the connection between two long-range enemy pieces interrupted, or else the path of a long-range piece (Queen Rook Bishop) to a crucial square is shutt off.
John Nunn - Learn Chess Tactics, 2004 Line-closing combinations commonly arise in two particular situations: pawn promotion and mating attacks.
Yakov Neishtadt - Test Your Tactical Ability, 1984 The idea behind blocking is to force (or to prompt) an opponent's piece to occupy a vitally important square, essential for more valuable piece (very often the king). This way the opponent's own forces create obstacles.
John Rice - Chess Wizardry The New ABC of Chess Problems, 1996 Obstruction occurs when a piece moves to a square so that another piece is prevented from occupying that square.
Step 4 Trainer Manual, 2005 Placing an enemy piece on a square that he badly needs is called blocking.
Arthur Yusupov - Build Up Your Chess 1: The Fundamentals, 2008 The smothered mate is a typical and effective combination. A single knight mates the king, whose own pieces are blocking its escape squares. A classic version, named after Lucena, contains a queen sacrifice in order to entice the rook to an unfavourable square. Sometimes the defending king is only partially hemmed in by its own pieces, but the opposing pieces control some escape squares. This version of smothered mate is not so well know, but often crops up in praxis.
It can happen that one's own piece (or pawn) prevents the realization of a profitable manoeuvre or a tactical blow. In such instances one should strive to vacate the square occupied by this piece (or the line which it is blocking) sometimes without baulking at sacrifices. Yakov Neishtadt - Test Your Tactical Ability, 1984
Arthur Yusupov - Build Up Your Chess 1: The Fundamentals, 2008 An especially spectacular tactic is an underpromotion, when the pawn does not promote to a queen, but to a rook, bishop or knight. The last case is the most frequent underpromotion, and is linked to a gain of tempo by check or to a knight fork.