6

As I understand chess rules, insufficient material means K vs. K, K vs. KB, or K vs. KN. (Correct me if I am wrong.)

But what about KB vs. KB when both bishops are in the same colored square? Am I right that that kind of position also will end up with a draw even if one player makes inaccurate moves?

Also, theoretically, there is a way to get position K vs. KBB where both bishops are in the same colored squares (if you promote your pawn to the bishop). Can this position also include to that rule?

What other theoretical positions may there be, which are 100% draws?

I ask this question as a programmer, not as a chess player, and the main purpose of this topic is to "teach" computers to understand the insufficient material rule.

1

2 Answers 2

10

As I understand chess rules insufficient material means K vs. K, K vs. KB, or K vs. KN.(Correct me if I am wrong)

Your understanding is wrong. the FIDE Laws of Chess have no "insufficient material" rule. What they do have is basically a "no helpmate" rule. Such a position is called a "dead position". That is to say that if there is no possible helpmate then the position is a draw. This is how it is phrased in article 5.2.2:

5.2.2 The game is drawn when a position has arisen in which neither player can checkmate the opponent’s king with any series of legal moves. The game is said to end in a ‘dead position’. This immediately ends the game, provided that the move producing the position was in accordance with Article 3 and Articles 4.2 – 4.7.

But what about KB vs. KB?

The rule you have to follow is that if you can place the pieces on the board in such a way that it is checkmate and you can move the pieces from their original positions when you have to make the decision to the checkmate position using only legal moves then it is not a draw.

So, for KB vs. KB where the bishops are the same colour you can quickly see that there is no possible checkmate position and it is a draw. Same for king plus any number of same squared bishops versus king plus bishop of the same colour.

2

KB vs KB when both bishops are of the same color it is automatically declared draw by insufficient material. The same with KBB vs KBBB (theoretically possible), as long as all bishops move on OR white squares OR all of them on black squares. If just one bishop moves on a different color, someone can still win.

4
  • With pure opposite colored bishops, any side can still win after blunders.
    – Jisu101
    Jan 6 at 8:36
  • Or take this FEN:
    – Jisu101
    Jan 6 at 8:38
  • 4k3/2p5/1pPp4/1P1Pp1p1/4PpP1/5P2/8/4K3 w - - 0 1 This is not counted as insufficient material, but lichess counts this as an immediate draw.
    – Jisu101
    Jan 6 at 8:39
  • 4
    Lichess does not count that as a draw, but it is practically a draw
    – Irsu85
    Jan 6 at 8:54

Not the answer you're looking for? Browse other questions tagged or ask your own question.