If these pieces still have natural predators on the board but they are unable to reach these red squares
It feels like there is something missing here.
Pieces can be blocked from reaching a certain square, don't they? Or, in the case of a Bishop of a different colour they will be unable to reach that square.
Pieces can be blocked from reaching a certain square, don't they? Or, in the case of a Bishop of a different colour they will be unable to reach that square.