Tablebase claim

An endgame tablebase is a precomputed database that knows the exact result of low-piece positions when both sides play optimally. It does not merely estimate the position: under the conditions represented by the tablebase, it classifies it as a win, draw, or loss.

The International Correspondence Chess Federation, abbreviated ICCF, allows a player to claim a win or draw when a tablebase covering up to seven pieces resolves the position. The limit counts both kings. This mechanism belongs to correspondence chess, where players exchange moves over long periods through the ICCF server, and is not a general claim available in an over-the-board game.

A player may claim only while it is that player's turn. The request may use the current position or state a proposed move and rely on the resulting position. The form must identify the tablebase ground. The server checks the position and, when the claim is correct, automatically sets the game result. A timely valid tablebase win claim also takes priority in ICCF over a draw claim under the 50-move rule, which normally rests on 50 moves by each player without a pawn move or capture.

An engine evaluation is not enough. An engine searches and estimates within finite resources; a covered tablebase provides an exhaustive result for its set of positions.