What is the maximum number of black and white pieces that are involved in a checkmate position? That is, if any piece were removed from the board, the position would not be checkmate because that piece is
- checking the king,
- blocking a square where the checked king can move,
- attacking an unoccupied square where the checked king can move, and/or
- preventing the king or other pieces from capturing or blocking the checking piece.
Note that both kings must also be involved in the position as described above.