Mate With 3 Knights

Question

How do I checkmate with 3 knights? I know 2 is a draw, but with 3 is not.

Answer 1

Here's an example of how to do it, plus some general guidance.

I can't find a single game in my 7 MM games database where it was managed, though a couple of players have tried it and come pretty close.

The key difficulty (beyond knowing what to do) is managing the timing; knights can't lose a move, so you can end up being ready to mate in a good position, but having one move too many (or being a move short).

I pulled this mate off once in a tournament game. My opponent is known for forcing his opponents to play out to mate, so I thought it might make the process a more interesting challenge. I promoted two pawns to knights to make a team of 3, and deliberately dropped a bishop in a check that forced capture. I solved the timing problem by keeping a spare rook away from the mating area, and when I found myself needing to lose a move with the king already netted, just shifted the rook. Then I was able to finish the mate.

There are two main types of mating pattern, the side mate and the corner mate. There are a couple of types of corner mate, but once you get close, you'll probably see the one that's eligible in your situation.

Here's a theoretical position I cooked up, to present the most challenging problem I could imagine. I used this as a training position.

[Event "?"]
[White "3 Knights Mate"]
[Result "0-1"]
[Annotator "K + 3N v K"]
[SetUp "1"]
[FEN "6n1/n7/4K3/8/8/4k3/8/1n6 b - - 0 1"]
[PlyCount "29"]

1... Kf4 {Mate in 14 from this position.  Note that the knights are almost in the corners, so this is as bad as it's likely to get without obstacles in the way. General move guidelines:  1. Close with the king before the knights _unless_:  a. You can close with check      b. You are defending     2. Surround the king at a distance first, so that whichever direction he runs, he will be moving towards more than 1 of your pieces.       3. Use self-defending "Tango" formations of 2 knights to create a fence to guide the king towards an edge or corner. Use the king to protect the 3rd knight.     4. Drive the king        a. first towards the other pieces,        b. then towards an edge       c. then _near_ but not _into_ a corner       5. Use zugzwang; checks aren't always necessary. Just make sure the defending king only has bad exits, ideally only one bad exit.     6. Learn the corner-zone mating maneuver.     7. Don't rush; the knights don't all come into contact with each other before at least the 10th move, and then only when they're on the 3rd rank/file from the edge, at the closest.     8. When the knights are together, keep your king next to them, or you'll lose one (and the win).      9. Don't worry about forcing the king onto only one square all the time.  Just make sure that if he has 2 squares to use near the edge, you're between him and the center, and can pivot to pen him in no matter which he chooses.} {flanking - Close with the king before the knights. Surround the king first.} 2. Kd5 Nc3+ {2. Close with check. (cutoff setup, closing with check.)} 3. Kc4 Nab5 {The 2 nearest knights form a Tango, and create a cutoff. Note how, with the king, they form an almost complete cutoff separating the queenside from the kingside.  The nearest hole is on d7.  That's where the defending king heads next.} 4. Kc5 Ke4 5. Kc6 Ne7+ $1 {Black sets up another knight tango, and splits the board into two zones.} 6. Kd7 Ncd5 {Tango} 7. Ke6 Kf4 $1 {Cutoff. Black uses zugzwang to push the king back. Checks are not essential.} 8. Kf7 (8. Kd7 Ke5 9. Ke8 Kf6 10. Kd7 Kf7 {transposes}) 8... Kf5 {The natural followup, closing with the king} 9. Kf8 Nd6 {cutoff along the edge again} 10. Kg7 Nf6 {This is the first piece to take up its final mating square.    The king and rear knight keep the white king from escaping via f7 or g6. The rear knight also maintains the cutoff behind the white king. The knights are on the same color squares as the corner they are forcing the defending king into.  The defending king has only 3 squares to choose from, including the corner, while he's in zugzwang.    The knights now start a series of maneuvers in which they form a kind of spinning wedge or Flying V; the center knight is towards the corner or edge, and the others flank it on the diagonals or the rank and file. This is Wedge 1.  "Don't Rush." This is the 10th move of the maneuvering, and the knights have only just come into contact on adjacent squares.} 11. Kh6 {Now that the rear knight's cutoff along the back rank is no longer vital, it can advance, relieving the king from denial of g5.} Nf7+ {Push the king onto the 2x2 corner square on the long diagonal, _not_ into the corner! He must be driven to the opposite edge square at the end of the 3rd file/rank. Note how the rear knight relieved the king from denial of g5.  The king will move onto e6, its final mating square, next move. The knights and king form a knight's move shape themselves. The knight on the corner of their formation attacks both the king and the corner they are targeting. It is a knight's move from the corner, itself, of course. The king forms the "tail" of the knight's move formation.  Next, it will "close the box" with the 3 knights.    The knight that just moved is weaving a zig-zag of 3 moves to mate on g6.    This is the 2nd Wedge.} 12. Kg7 Ke6 $22 {(support, zugzwang) The black king moves onto its final mating square, closing the box with the 3 knights.    Now the white king is trapped, and has only one move.} 13. Kf8 Ne5 {Quiet move. Pull the first of the two knights nearest the edge back 2 squares until it's behind the king, __without check_.  Note that mate is not immediate; the knight must redeploy.  This is the 2nd move of the knights 3-move zig-zag maneuver to give mate. You are "flipping the box", putting the two knights that are closest to the defending king on the opposite side of the box. (3rd Wedge)} 14. Kg7 Nf5+ {Pull the other knight back 2 squares _with check_, leaving only the corner square and the edge square free, but setting a new cutoff on the other edge.    You have "flipped the box". This is the final formation to give mate.    (4th Wedge)} 15. Kf8 Ng6# {The farthest knight "opens the box" to give the mate.     (Oh, and this is the 5th Wedge in a row that the knights have formed.)} 0-1