Candidate Move: Chess concept and calculation
Candidate Move
Definition
A candidate move is any move that a player singles out for serious, concrete calculation during a game or post-game analysis. Rather than analyzing every legal possibility (an impossible task at the board), the player first generates a short list of promising alternatives and then investigates each one in depth. The term was popularized by Soviet Grandmaster and author Alexander Kotov in his classic 1971 book “Think Like a Grandmaster,” where he presented the method now known as the tree of analysis: pick your candidate moves, calculate each branch as far as necessary, compare the final positions, and only then decide.
Why It Matters
- Efficiency: Narrowing the search to 2–5 moves saves precious clock time and mental energy, especially in complex positions.
- Error-reduction: A systematic list prevents “move blindness”—overlooking a strong reply or tactical resource.
- Transferable skill: The same habit is used by engines (through move ordering and pruning) and by top players during opening preparation and post-mortem analysis.
Typical Process for Selecting Candidate Moves
- Scan the position for forcing moves: checks, captures, and threats (often abbreviated “CCT”).
- Add strategically logical plans—e.g., improving piece placement, occupying open files, or creating passed pawns.
- Eliminate obviously inferior moves (material loss, immediate refutation).
- Calculate each remaining candidate in turn, building a mental tree of variations.
- Compare evaluations and make the final choice.
Strategic & Historical Significance
Before Kotov’s formal description, masters obviously used a similar mental process, but his articulation gave generations of players—from club level to World Champions—a concrete thinking model. The “candidate move” concept is now ubiquitous in chess literature, coaching, and even software design: engines like Stockfish sort moves by heuristics (e.g. the history heuristic) to analyze the most likely “candidates” first, gaining speed through alpha-beta pruning.
Illustrative Examples
1. Opening Choice: Ruy Lopez, Exchange or Retreat?
After 1. e4 e5 2. Nf3 Nc6 3. Bb5 a6, White’s standard candidate moves are:
- 4. Bxc6 (Exchange Variation)
- 4. Ba4 (Main Line)
- 4. Be2 (Quiet Retreat)
Each leads to a distinct strategic battle, so a practical player quickly weighs style, preparation, and opponent tendencies before selecting one line for deeper calculation.
2. Tactical Shot: Kasparov – Topalov, Wijk aan Zee 1999
In the celebrated position after 23… Rxd4, Kasparov found the dazzling candidate 24. Rxd4! (initiating a legendary 15-move combination) by first listing forcing possibilities—discovering that the exchange sacrifice opened crushing lines against the Black king.
3. Endgame Precision: Finding the Only Move
In certain technical endings, there may be only one path to salvation. Identifying that sole candidate is half the battle; calculation confirms it. A famous example occurs in the 1953 candidates tournament game Najdorf – Kotov, where Black had to spot the narrow drawing resource 62… Kg3!, the only candidate that held the fortress.
Common Heuristics for Generating Candidates
- Checks, Captures, Threats (CCT): Start with moves that limit the opponent’s reply.
- “Worst-placed piece first” rule: Improve your most inactive piece.
- Pawn breaks: Look for opening lines or creating passed pawns.
- Comparative counting: Consider material imbalances or piece activity to justify sacrifices.
Interesting Facts & Anecdotes
- GM Kotov admitted he sometimes violated his own advice and “got lost in the forest” of variations, coining the humorous phrase “Kotov’s Syndrome” for moments when a player spends a long time calculating one branch, realizes it fails, and must move quickly without adequate analysis of the remaining candidates.
- World Champion Vishy Anand reportedly trained by writing down candidate moves on paper during practice games to sharpen discipline— a technique echoed in many chess academies today.
- Modern neural-network engines like Leela Chess Zero still rely on candidate filtering. Although they evaluate positions rather than calculate brute-force lines, they restrict search to the most promising “policy” moves suggested by the network.
Quick Self-Test
In the diagram (White to move), list at least three candidate moves before you calculate! Then compare with a friend or coach.
Takeaway
Mastering the art of selecting and evaluating candidate moves transforms raw calculation into purposeful, organized thinking. Whether you’re deciding between sharp tactical blows or subtle strategic plans, the method remains the same: identify, calculate, compare, decide.