Insufficient material
Insufficient material is the situation where the pieces left on the board could not produce checkmate for either side even if the opponent cooperated fully, so the position is dead and the game ends drawn.
Also called: dead position by material
The test is not whether a player can force mate but whether any mate exists at all. Picture the weaker side cooperating, walking into a corner and blocking its own king, and ask whether the stronger side could then deliver checkmate. If even that cannot happen, the material is insufficient and play stops.
With no pawns left, only a few material balances are dead in this sense: a lone king against a lone king, a lone king against a king with a single bishop or a single knight, and positions where every bishop on the board, on both sides, travels on squares of one color. That last case is the one in the example.
Many endings are not dead even though nobody could ever win them by force. Two knights cannot drive a lone king to mate, yet a mate exists if the defender blunders, so the game continues. The same is true of a knight against a knight, or of bishops on opposite colors, because the defending king could in theory be hemmed in by its own piece. A pawn on the board usually keeps the game alive too, since it may promote.
The rule matters most on the clock. A player whose flag falls still draws if the opponent has no possible way to mate. If the opponent keeps even a knight while you still have pieces of your own that could block your king in, a mate is possible and the flag fall loses.
Also worth reading is Bishop and knight checkmate. Bishop and knight checkmate is the ending in which a king, a bishop and a knight force mate against a lone king, which must be driven into a corner of the bishop's color.
A neighboring idea is Dead position. A dead position is one in which checkmate can no longer happen for either side, however the moves go and however cooperative the players are, and the game ends as a draw the moment it arises.
A neighboring idea is Insufficient mating material. Insufficient mating material describes a position in which neither side has enough pieces to deliver checkmate by any legal sequence, which the Laws treat as a dead position and a draw.
Endgame ideas like "Insufficient material" are won or lost on small details, which a coach can check in your own games. The first lesson with George Li is where that review starts.
Related terms
A dead position is one in which checkmate can no longer happen for either side, however the moves go and however cooperative the players are, and the game ends as a draw the moment it arises.
Insufficient mating material describes a position in which neither side has enough pieces to deliver checkmate by any legal sequence, which the Laws treat as a dead position and a draw.
Stalemate is a draw that occurs when the side on move has no legal move at all while its king is not attacked, so the game ends on the spot with half a point to each player.
Opposite-colored bishops are bishops that run on different shades of squares, so neither side can attack or exchange the other's bishop, which makes endings with them notoriously drawish even when one side is a pawn or two ahead.
Bishop and knight checkmate is the ending in which a king, a bishop and a knight force mate against a lone king, which must be driven into a corner of the bishop's color.
The two knights endgame is the ending with a king and two knights against a bare king, in which checkmate cannot be forced although it can sometimes arise by mistake.
Guides that go further
What to decide first, the questions to ask, what a first lesson should show and the red flags to avoid.
How much does chess coaching cost?
Published rates for private, group and subscription chess coaching, with the source and the date of each.
A game review, a read on your level and a written study plan from George Li.
Want to spot this in your own games?
A first lesson starts with your games: George reviews them and builds a study plan around what he finds.