How to Force mate with Three Knights
Everyone knows that you can force mate with three Knights, but do you know how? Wouldn't it be cool to have this in your bag of tricks to use on opponents who just won't resign? Of course it would!
I will show you a method, complete with stragetic milestones and one or two tools that will get you there. Consider the position below, black to move. As White, you have 50 moves to force mate. Tablebase says that with Black to move, white can force mate in 20, but it's rather difficult to calculate with that kind depth and nuance.
The best thing to do is to have a method by which to organize and coordinate the three horses. Now, the first order of business with the pieces in corners like that is to avoid getting one of them trapped. If the black King were on d4, d5, or e5, the game would be a draw because it would be possible to trap the Knight in the nearest corner. That's why the K is on e4.
The game below is me playing vs Tablebase. Thus Black plays perfectly, and I play according to my method.
Strategic Goal #1: Get the Knights safely out of the corners.
Strategic Tool #1: Connect loose Knights so they protect each other
When loose Knights in transition are connected, the enemy King is harmless.
Strategic Tool #2: Coordinate the Knights by getting them into the Delta formation.
There is really only one rule about assuming this formation. That is that the enemy King must be far enough away so that it can't make contact with any Knight in the formation. Once the King is outside the triangle of Knights, it will never make contact with a Knight again, ever. The Delta sets up a "force field" that the King cannot get through.
Strategic Goal #2: Gain control of the center. This will force the lone King toward the edge of the board.
Strategic Goal #3. Push the enemy King to the edge of the board, and keep it there.
Strategic Tool #3. The Tunnel of Doom.
When two or more Knights sit next to each other on the 5th rank, they automatically control four (or six) squares along the 7th rank. Since the King is on the 8th rank, behind those squares, it's confined to the edge.
Strategic Goal #4. Use your King to push the enemy down the Tunnel of Doom to force mate.
And now for completeness, here is the whole process from start to finish. If you take the time to understand this method, you can apply it to any KNNN vs K position
