Tactics in chess is the coordinated task in realizing short-term advantage or equilibration, yielding in mate attack, material gain, or forcing draw in inferior positions. Tactical moves either change the material balance immediately, or in a wider sense, threaten to win material and/or checkmate considering certain tactical motives. Often tactics of several types are conjoined in a combination including short-term sacrifices. While tactics is most often a domain of the middlegame, it already appears in various opening lines, specially gambits, very early in the game. During the endgame, technical or strategical play seems to dominate, but there are many tactical motives like pursuits, stalemate, zugzwang, pawns breakthrough and passed pawns to name a few, to be considered there as well.
- Richard Teichmann: Chess is 99 percent tactics. 
- Gerald Abrahams: The tactician knows what to do when there is something to do; whereas the strategian knows what to do when there is nothing to do.
- Max Euwe: Strategy requires thought, tactics require observation.
Tactical positions usually involve tension and offer tactical motives and moves, possibilities to attack and counter attack kings or valuable pieces, often one tempo is decisive. Tactical positions require concrete calculation rather than strategic long-range planning, and that is what makes most chess programs so strong compared to human players in these kind of positions. On the other hand, certain chess tactics, even if a domain of the computers, are still too complicated and deep for chess programs to solve in a reasonable time frame, and require hours or days of computer and/or human master analysis, to eventually discover the "truth of the position".
Tactics in Chess Programs
Todays rather selective chess programs almost perform an exhaustive search of immediate tactical moves, and even tend to extend them, or at least to don't prune or reduce them, and further perform a quiescence search at horizon nodes. If the iterative deepening search-routine of a chess program "suddenly" recognizes a "big" score jump at the root, there is almost certainly chess tactics involved.
Search trees of highly tactical positions tend to be narrow and deep. Often, replies are singular due to forced recaptures or check evasions, triggering for instance check extensions, recapture extensions, singular extensions or one reply extensions. The somehow complement set of non-tactical moves may be reduced by null move pruning, multi-cut and late move reductions. Tactics is therefor covered by search, even with rudimentary evaluation (better with some king safety terms involved) - but positional evaluation and strategical knowledge is necessary to drive the program into tactical positions, where it might out-search the opponent due to its superior search. Anyway, some programs consider some tactical motives in their evaluation or search control, which are usually not subject of a quiescence search, to become aware before they occur two or more plies behind the horizon, especially in PV-nodes and to avoid standing pat if the opponent has some threats.
Some programs consider some tactical features in evaluation, i.e. penalties for pieces en prise of either side . One may also consider too many hanging pieces, even if not actually attacked but the opponent has resources to perform double attacks. Pinned pieces may subject of respective penalties in evaluation as well.
Terms and Motives
- Annihilation of Defense
- Attack and Defense
- Demolition of Pawns
- Discovered Attack
- Discovered Check
- Double Attack
- Double Check
- En prise
- Hanging Piece
- Loose Piece
- Pawns Breakthrough
- Passed Pawn
- Pursuit (perpetual attack)
- Space Clearance
- Tactical Moves
- Checks and Pinned Pieces (Bitboards)
- Intersection Squares
- Knight Forks (Bitboards)
- Mate at a Glance
- Mate Search
- Pattern Recognition
- Quiescence Search
- X-ray Attacks (Bitboards)
Tactical Pattern Programs
- Nikolai Krogius, with A. Livsic, Bruno Parma & Mark Tajmanov (1980). Encyclopedia of Chess Middlegames: Combinations. Chess Informant, amazon
- Yuri Averbakh (1985). Chess Tactics for Advanced Players. Pergamon Press, 2008 edition by Labate Chess, 2012 edition by Ishi Press with introduction by Sam Sloan
- Jenő Bán (1997). The tactics of endgames. Dover Publications, ISBN-13: 978-0486297057, amazon.com
- Claus Dieter Meyer, Karsten Müller (2002). The Magic of Chess Tactics. Russell Enterprises, ISBN-13: 978-1888690149, Rezension from Schachgemeinschaft Caissa-Rochade Kuppenheim 1979 e. V. (German), amazon, DVD from ChessBase
- Yasser Seirawan (2003). Winning Chess Tactics, Everyman Chess, ISBN-13: 978-1857443332, amazon
- John Nunn (2003). Learn Chess Tactics. Gambit Publications, ISBN-13: 978-1901983982, amazon
- John Nunn (2003). Tactical Chess Endings. Batsford, ISBN-13: 978-0713459371, amazon
- Paul Littlewood (2004). Chess Tactics. Batsford Chess Book, ISBN-13: 978-0713489347, Reviewed by John Donaldson, amazon
- Susan Polgar (2006). Chess Tactics for Champions. Random House Puzzles & Games, ISBN-13: 978-0812936711, Book Review from Chess.com, amazon
- Jack Good (1968). A Five-Year Plan for Automatic Chess. Machine Intelligence II pp. 110-115, excerpts reprinted in Computer Chess Compendium, covering Quiescence, Turbulence, and Agitation 
- Hans Berliner (1974). Chess as Problem Solving: The Development of a Tactics Analyser. Ph.D. thesis, Carnegie Mellon University
- Hans Berliner (1977). A Representation and Some Mechanisms for a Problem-Solving Chess Program. Advances in Computer Chess 1
- Alexander Szabo (1984). Computer-Chess Tactics and Strategy. M.Sc. Thesis, University of British Columbia
- Steven Walczak (1992). Pattern-Based Tactical Planning. IJPRAI 6(5)
- Steven Walczak, Douglas D. Dankel II (1993). Acquiring Tactical and Strategic Knowledge with a Generalized Method for Chunking of Game Pieces. International Journal of Intelligent Systems 8 (2), 249-270.
- Alexis Drogoul (1993, 1995). When Ants Play Chess (Or Can Strategies Emerge From Tactical Behaviors?) MAAMAW ’93, CiteSeerX pdf
- Some Computer Chess Questions by MWells, rgcc, September 1, 1996
- Need ideas on recognize 'tactics' from game database by Fermin Serrano, CCC, August 22, 2014
- Is chess still 99% tactics? by Alvaro Cardoso, CCC, January 11, 2018
- delaying tactics: prune or extend? by Harm Geert Muller, CCC, March 10, 2019 » Selectivity
- Positional and Tactical by Ferdinand Mosca, CCC, April 11, 2019
- Chess Tactics by Ward Farnsworth
- CTS - Chess Tactics Server
- Chess Tactics Index - 15 Tactics, From Battery Attacks, to X-Ray Attacks
- Tactical Play in Chess by Mark Weeks
- ChessWorld.net's Tactics technical paper suite!
- Mikhail Tal from Wikipedia, Photo by Gerhard Hund, European Championship 1961 at Oberhausen ]
- Chess - Wikiquote
- Chess Corner - Chess Quotes
- Is chess still 99% tactics? by Alvaro Cardoso, CCC, January 11, 2018
- Programmer Stuff by Ed Schröder, (see hanging pieces)
- David Levy, Computer Chess Compendium, Chapter 3, Position Evaluation pp. 112: Perhaps non-linear evaluation functions will become popular at some future date, in which case some of Good's ideas will come into their own.