Candidate moves in chess
Candidate Moves
Definition
In chess thinking, candidate moves are the short list of seemingly promising moves a player selects for deeper calculation in a given position. Rather than analysing every legal move (which is impractical even for grandmasters), the player first performs a quick scan, picks two to five attractive alternatives, and then examines each branch in detail. The concept was popularised by Soviet GM Alexander Kotov in his classic “Think Like a Grandmaster” (1971), where he presented the “Kotov tree” of analysis: 1) identify candidate moves, 2) calculate each line once, 3) compare the results.
Origin & Historical Significance
While strong players had used an informal version of the idea for centuries, Kotov was the first to codify it and give it a name. His teachings filtered through the Soviet school, shaping the thinking process of legends such as Anatoly Karpov and Garry Kasparov. Today, “candidate moves” is standard vocabulary in coaching manuals, engine design (move ordering), and even popular streaming.
Why They Matter Strategically
- Efficiency – Limits the search tree so clock time is spent on critical lines.
- Error-reduction – A systematic scan helps prevent “blind-spots,” such as overlooking a forcing reply.
- Focus – Encourages a shift from move-by-move calculation to plan-based thinking (“What am I trying to achieve?”).
How Players Choose Candidate Moves
- Forcing moves first: checks, captures and threats (commonly abbreviated CCT).
- Moves that improve piece activity: centralisation, open files, outposts.
- Defensive resources: interpositions, counter-attacks, perpetual checks.
- Quiet but strategic ideas: prophylaxis (e.g., 1…h6 stopping Bg5), pawn breaks, improving king safety.
Usage in Practical Play
Over-the-board, a master might spend the first 30 seconds of a critical position merely listing candidate moves in the mind’s eye before any calculation starts. In correspondence or engine-assisted analysis, candidates direct what lines to explore with software. Even bullet specialists use a lightning-fast version: checks and captures are “pre-selected” almost automatically.
Illustrative Example
Position after 17…Re8 in Kasparov – Topalov, Wijk aan Zee 1999, white to move (material equal, white pieces more active). Kasparov’s thought process (reconstructed from his notes):
- Candidate 1: 18.Nxf7! – a spectacular knight sacrifice exploiting the pin on the e-file.
- Candidate 2: 18.Rxe8+ Qxe8 19.Qxd5 – wins a pawn but allows counterplay.
- Candidate 3: 18.Qb3 – a quieter buildup.
After calculating, he chose 18.Nxf7!!, the start of one of the most famous tactical combinations of the modern era, proving how a correct candidate list can uncover brilliancies invisible at first glance. [[Pgn|1. e4 d6 2. d4 Nf6 3. Nc3 g6 4. Be3 Bg7 5. Qd2 c6 6. f3 b5 7. Nge2 Nbd7 8. Bh6 Bxh6 9. Qxh6 Bb7 10. a3 e5 11. O-O-O Qe7 12. Kb1 a6 13. Nc1 exd4 14. Rxd4 c5 15. Rd1 Nb6 16. Nb3 O-O-O 17. g3 Re8 18. Nxf7! — 1-0]]
Candidate Moves & Computer Chess
Engines also use a
candidate-selection/ordering phase, scoring moves by heuristics
(history tables, killer moves, MVV-LVA) before running alpha-beta search.
Modern neural nets like AlphaZero skip explicit move lists but still
allocate more playouts to their internal “preferred” moves—the same idea in
new clothing.
Common Pitfalls
- Too few candidates: missing a game-saving resource.
- Too many candidates: time trouble through analysis paralysis.
- Bias: favouring aesthetically pleasing moves over objectively strong ones.
Interesting Facts & Anecdotes
• Kotov admitted that while advising others to calculate each line only
once, he himself would sometimes redo lines “for safety,”
proving even authors struggle with their own rules.
• In the famous “Game of the Century”
(Fischer – Byrne, New York 1956) the 13-year-old Fischer reportedly
considered only three candidate moves at the key moment—
one of which was the immortal 17…Be6!! leading to his queen sacrifice.
• Hikaru Nakamura has quipped on stream that his blitz candidate
list is “anything that gives me practical chances and pre-moves well,”
showing the concept adapts to every time-control.