KoBul kings - fairy chess power-switch

KoBul kings

Definition

KoBul kings is a popular fairy-chess condition used in chess composition. Under KoBul kings, each side’s king dynamically changes its movement power according to the last captured piece of its own color. The condition was introduced by Bulgarian problemist Diyan Kostadinov (the name “KoBul” is a nod to Kostadinov + Bulgaria).

• When a non-pawn White piece is captured, the White king immediately gains the movement of that captured piece in addition to its normal king step. The same applies for Black.
• When a pawn of a side is captured, that side’s king loses any extra power and reverts to the normal king move.
• The king always remains royal: it cannot move into check and may not pass through attacked squares. Checks and mates must be judged with the king’s current, enhanced power.
• Captured promoted pieces count by their current type. For example, if a promoted white rook (from a pawn) is captured, the White king becomes “rook-king” (king + rook move).
• Castling follows usual legality in problems (if allowed at all); KoBul power does not grant special castling rights.

How it is used in chess

KoBul kings does not appear in over-the-board play; it is a fairy condition for composed problems. It is frequently combined with helpmates, selfmates, and other fairy conditions to produce paradoxical, thematic mates and subtle move-order questions.

• Helpmates and selfmates: composers engineer specific captures to “program” the enemy king’s power for the eventual mate.
• Thematic switches: the identity of the last captured piece determines the king’s power, so small move-order changes completely alter the solution.
• Dual avoidance: only one capture order yields the intended royal power at the critical moment, eliminating dual solutions.
• Synergy with other conditions: works well with Circe and Madrasi to create striking paradoxes and model mates.

Strategic and historical significance

Introduced around 2010 by Diyan Kostadinov, KoBul kings quickly gained traction in the fairy-composition community for enabling rich “power-switch” play. It allows composers to script the king’s role—from a “knight-king” that jumps to safety, to a “rook-king” that slides across files in one move, to a “queen-king” that controls long lines—then reset it with a pawn capture. This condition has inspired dedicated composing tourneys and numerous award-winning problems.

Examples

Below are simplified, instructive scenarios. Remember: these illustrate the logic of KoBul kings; specific legality (especially checks on the path of a sliding king) must be verified square by square, just as in orthodox chess.

Example 1: Rook-power rescue
Position: White king e1, white rook a1; Black king e8, black rook a8. Black to move. FEN: 4k3/r7/8/8/8/8/8/R3K3 b - - 0 1.

• 1... Rxa1+ captures a white rook. Under KoBul, the White king becomes a rook-king (king + rook move).
• Now, if safe, White could in principle slide the king several squares along a rank/file in one move (e.g., e1–e4) to escape check—something impossible in orthodox chess.

Example 2: Knight-power leap
Position sketch: White king g1; White pieces include a knight on f3. Black arranges ...Bxf3, capturing White’s knight. Immediately, the White king becomes a knight-king (king + knight move). If Black was threatening mate on the back rank, Kg1–e2 (a knight jump) might suddenly defend or counterattack, a resource unavailable without KoBul.

Example 3: Pawn reset
Imagine White’s king currently has bishop-power because a white bishop was captured earlier. After Black plays ...exd3 capturing a white pawn, White’s king instantly reverts to a normal king (pawn capture resets power). Composers exploit this to time when the defending king loses long-range options, enabling precise mating nets.

Miniature demonstration of a plan
Idea: White wants the Black king to have rook-power to block its own escape squares on a file. White sacrifices a rook for something like ...R×R to “arm” the Black king with rook power, then engineers a mate where any rook-slide by the king would cross attacked squares—illegal for the royal piece.

Problem-composition themes and tips

• Track the last captured piece of each color; it defines the kings’ current powers.
• Pawn captures reset that side’s king to normal—useful for timing a mating net.
• Sliding royal moves (rook-/bishop-/queen-power) cannot pass through or land on attacked squares; treat every traversed square as if the king must remain safe there.
• Look for thematic pairs: one line gives the opponent a “bad” power (e.g., rook-king trapped on a file); a second line gives a “good” power (e.g., knight-king escapes), explaining why only the intended capture order works.
• KoBul kings shines in Helpmates and Selfmates, but also appears in proof games and other genres of Fairy chess.

Interesting facts and anecdotes

• Origin: Credited to Diyan Kostadinov (Bulgaria). The “KoBul” label became closely associated with his composing work and the Bulgarian school.
• Variants exist. You may encounter “Super KoBul Kings” or “Reversed KoBul Kings” in tourneys; always check the announcement for the exact rule set.
• Common tasks feature multiple, distinct royal powers (Q, R, B, N) shown in different phases, with a pawn-capture “reset” cleverly integrated to control timing.

Rules checklist (quick reference)

• Non-pawn of a color captured → that color’s king gains the captured piece’s move (in addition to K-step).
• Pawn of a color captured → that color’s king reverts to normal king move.
• King remains royal; no moving into or through check; normal check/mate definitions apply but use the current king power.
• Promoted piece captured → the king takes that promoted piece’s power.
• Castling is unaffected by KoBul power (if castling is allowed in the problem, standard conditions apply).

Related terms and further exploration

• Fairy composition basics: Fairy chess, Condition, Fairy pieces
• Popular companion conditions: Circe, Madrasi
• Problem genres: Helpmate, Selfmate, Proof game
• People and roles: Chess composer, Problemist, Solver

Why composers love KoBul kings

From an aesthetic viewpoint, KoBul kings creates crisp cause-and-effect between captures and royal mobility. It offers clean thematic control—composers can “program” the king’s capabilities by orchestrating which unit is captured and when—yielding elegant model mates, paradoxical defenses, and memorable switchbacks that are difficult or impossible to achieve in orthodox settings.