The border-line to block the pawn in order to be able to execute mating attack, is pictured in the following diagram. The position is won provided the rook or central pawn has been stopped at least on the fourth rank; the c- or f-pawn must be stopped at the latest on the fifth, whilst b- or g-pawn must be stopped at least on the sixth rank. A pawn on the b- or g-file is also unpleasant because the stronger side has more difficulty driving the enemy king towards the rim of the board since the blocking knight does not co-operate well in the task of addittionally limiting the space. The task of the stronger side is all the more difficult the farther away the enemy king is from the corner of the chess-board. If the king is also far away from the blocking knight, then great skill must be demonstrated in order to gradually restrain the enemy king and eventually enclose it in one of the corners. Given the most accurate defence this process may take very long time since the enemy king must be pushed one square nearer the rim of the board at a time which is possible only after the king has run over the whole board in a circuitous fashion and finally reaching the obstacle erected by the blocking knight. This complex strategy of pushing away the enemy king requires true mastery. We will examine the position with a central pawn, elaborated in great detail by V. Chekhover.
The position is won provided the rook or central pawn has been stopped at least on the fourth rank; the c- or f-pawn must be stopped at the latest on the fifth, whilst b- or g-pawn must be stopped at least on the sixth rank.