try instead: 1. Nf8 Kg8 2. Nd7 Kh8 3. Nd6 Kg8 4. Nf6+ and now if Black moves 4...Kh8?? then 5.Nf7# is checkmate, but if Black moves 4... Kf8! then White has made no progress. Johann Berger gave this position, a draw with either side to move. With White to move: 1. Nf5 Kh8 2. Ng5 Kg8 3. Ne7+ Kf8! (Black just avoids 3...Kh8? which leads to a checkmate on the next move with 4.Nf7#) 4. Kf6 Ke8 and White has made no progress. With Black to move: 1... Kh8 2. Nf7+ Kg8 3. Nh6+ Kh8 4. Ng5 gives stalemate. On the edge There are also checkmate positions with the inferior side's king on the edge of the board (instead of the corner), but again they cannot be forced ( + ). In the position at right, White can try 1. Nb6+, hoping for 1...Kd8?? 2.Ne6#. Black can easily avoid this with, for example, 1... Kc7. This possible checkmate is the basis of some problems (see below). Examples from games In this position from a 1949 game between Pal Benko and David Bronstein, Black underpromoted to a knight. Black did not promote to a queen or any other piece because White could fork Black's king and his newly promoted piece (e.g. 104...f1=Q 105.Ne3+) immediately after the promotion. 104...f1=N+ 105. Kc3 Kf3. White made the humorous move 106. Nh2+ forking Black's king and knight, but sacrificing the knight. Black responded 106... Nxh2 and a draw was agreed. (A draw by threefold repetition could have been claimed on move 78 and at other times.) Another example is the eighth game of the 1981 World Chess Championship match between Anatoly Karpov and Viktor Korchnoi. Black forces a draw by 80... Nf7! 81. h7 Ng5! 82. Ne7+ Kb7 83. Nxg6 Nxh7 84. Nxh7 draw Three knights Three knights and a king can force checkmate against a lone king within twenty moves (unless the defending king can win one of the knights). Also, a complete computational retrograde analysis revealed that they can force checkmate only on the edge of the board. Two knights versus a pawn In some positions with two knights versus a pawn, the knights can force checkmate by gaining a tempo when the pawn has to move. Troitsky line Even though two knights cannot force checkmate (with the help of their king) against a lone king (with the exception of positions where