Editing Checkmate (section)

===King and two bishops {{anchor|Two bishops}}===
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The '''two bishops checkmate''' is the checkmate of a [[bare king|lone]] king by the opponent's two bishops and king.{{efn|"Against one knight or one bishop the defender cannot lose even if he wants to."{{sfn|Fine|1979|p=1}}}} 
The superior side is able to {{chessgloss|forced move|drive}} the lone king into a corner and {{chessgloss|forced mate|force mate}} using the two bishops and king collaboratively. The only stipulation is that the two bishops must move on opposite-colored squares.{{efn|Only an [[underpromotion]] can result in bishops on same-colored squares.}}{{sfn|Fine|1979|p=4|ps=, "Two bishops of the same color cannot administer mate; a mating position is not even conceivable. The same holds true of nine (or more!) bishops all of one color."}} Accomplishing the mate requires a maximum of 19 moves.
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|+ Checkmates with two bishops 
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|Checkmate via forcing opponent's king in a corner
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|Checkmate via a side square adjacent to a corner square
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The king and bishops cooperate to drive the enemy king to an edge of the board, and then into a corner to deliver the mate.{{sfn|Fine|1979|p=1}} "The process, though a bit lengthy, is fascinating because it gives us a glimpse of the power of the two bishops on the open board."<ref>{{cite book |last=Reinfeld |first=Fred |authorlink=Fred Reinfeld |title=The Complete Chess Course |publisher=[[Doubleday (publisher)|Doubleday & Company, Inc]] |year=1959 |page=330 |isbn=0385004648 }}</ref>

Three basic checkmate positions are possible via the two bishops checkmate.{{sfn|Fine|1979|p=3}} The first is a checkmate in the corner. The second position is a checkmate on a side square next to the corner square (this position can theoretically occur anywhere along an edge, but can only be forced adjacent to a corner). With the side with the bishops to move, checkmate can be forced in at most nineteen moves,<ref name=muller01p17>{{harvnb|Müller|Lamprecht|2001|p=17}}</ref> except in some very rare positions (0.03% of the possible positions).<ref name=speel7>{{harvnb|Speelman|Tisdall|Wade|1993|p=7}}</ref> The third checkmate position is possible but not forceable.{{sfn|Fine|1979|p=3}}

It is not too difficult for two bishops to force checkmate, with the aid of their king. Two principles apply:
{{unordered list|style=list-style-position:inside
 |The bishops are best when they are near the {{chessgloss|center}} of the board and on adjacent diagonals. This cuts off the opposing king.
 |The king must be used aggressively, in conjunction with the bishops.
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{{Clear}}

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|From Seirawan
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|Two bishops and king can force mate. 
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In the position from Seirawan, White wins by first forcing the black king to the side of the board, then to a corner, and then checkmates. It can be any side of the board and any corner. The process is:

:'''1. Ke2 Ke4''' (Black tries to keep his king near the center) '''2. Be3 Ke5''' (forcing the king back, which is done often) '''3. Kd3 Kd5 4. Bd4 Ke6 5. Ke4 Kd6''' (Black tries a different approach to stay near the center) '''6. Bc4''' (White has a fine position; the bishops are centralized and the king is active) '''6... Kc6''' (Black avoids going toward the side) '''7. Ke5 Kd7''' (Black is trying to avoid the a8-corner) '''8. Bd5''' (keeping the black king off c6) '''8... Kc7 9. Bc5 Kd7 10. Bd6!''' (an important move that forces the king to the edge of the board) '''10... Ke8''' (Black is still avoiding the corner) '''11. Ke6''' (now the black king cannot get off the edge of the board) '''11... Kd8 12. Bc6''' (forcing the king toward the corner) '''12... Kc8''' (Black's king is confined to c8 and d8; the white king must cover a7 and b7) '''13. Kd5''' (13. Ke7{{chesspunc|?}} is [[stalemate]]) '''13... Kd8 14. Kc5 Kc8 15. Kb6 Kd8''' (now White must allow the king to move into the corner) '''16. Bc5 Kc8 17. Be7!''' (an important move that forces the king toward the corner) '''17... Kb8 18. Bd7!''' (the same principle as the previous move) '''18... Ka8 19. Bd8''' (White must make a move that gives up a [[tempo (chess)|tempo]]; this move is such a move, along with Bc5, Bf8, Be6, or Ka6) '''19... Kb8 20. Bc7+ Ka8 21. Bc6#''' (as the first diagram in this section).<ref>{{harvnb|Seirawan|2003|pp=5–7}}</ref>

This is not the shortest forced checkmate from this position. Müller and Lamprecht give a fifteen-move solution; however, it contains an inaccurate move by Black (according to [[endgame tablebase]]s).<ref name=muller01p17 />

'''Avoid stalemate'''
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|1.Kb6 would be stalemate.
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<br />One example of a stalemate is this position, where 1.Kb6 (marked with the x) would be stalemate.<ref>{{harvnb|Silman|2007|p=191}}</ref>
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