Tactics

The State regime groups tactical motifs that describe a relationship or constraint present in the position under examination. This fact can be established by examining the position and, where required by the motif’s definition, legal continuations. Creating this state and exploiting it are distinct actions.

• Hanging Piece6 variantsA piece under attack with no legal defender, so it can be won at once.
• Overloading3 variantsA single defender charged with more duties than it can keep.
• Pin8 variantsA piece is restrained because moving it would expose a more valuable piece, or the king, behind it on the same line.
• Trapped Piece4 variantsA piece with no safe square, so it can be won wherever it goes.

The Goal regime groups tactical motifs whose claim concerns the achievement of a goal specific to the mechanism described. That goal is established when the side pursuing it can achieve it against every legal defense, under the conditions defined for the motif. The claim therefore comprises both the mechanism and its outcome and cannot be reduced to the configuration produced after a move.

• Discovered Attack11 variantsA piece moves aside to reveal an attack from a long-range piece behind it.
• Fork16 variantsA single piece attacks two or more targets at once, so the defender cannot save them all.
• Interference6 variantsInterposing a piece to cut an enemy defensive line.
• Skewer11 variantsA valuable piece is attacked along a line and must move, which exposes a less valuable piece behind it.

The Instrumental regime groups tactical motifs that describe the causal role of a move or mechanism in achieving a goal distinct from the means employed. This role is not necessarily unique. Establishing it requires establishing both the goal and its causal connection to the means, under the conditions specific to the motif. It characterizes the means used in the combination.

• AttractionA forcing move that draws a piece onto a square where a tactic becomes possible.
• Deflection6 variantsA forcing move that drives a defending piece away from a duty it was performing.
• Self-Interference1 variantA defender is forced to interpose, and the interposition cuts one of its own defensive lines.
• SacrificeA move gives up material, judged by the full sequence of exchanges on the square it touches.
• Double Check5 variantsTwo pieces give check at once, so the king must move, because nothing else can answer both checks.