Checkmating with 2 Knights and a Bishop!!
Now this a tricky one! You cannot force checkmate on an empty board with just 2 knights, but you can if you have a bishop to help things along...
Still to this date I have not mastered the technique, even though I discovered the following technique myself, I am not sure at all if it is theory, or if there is a hard and fast definitive solution like checkmating with 2 bishops (see my previous blog post ) but my curiosity got the better of me, and discovered that checkmate can be forced in any of the 4 corners, but it depends on what colour-squared bishop you have... if you have a light-squared bishop, you can ONLY checkmate by force in the top-left and bottom-right corners, if you have a dark-squared bishop, you can ONLY force checkmate in the top-right and bottom-left corners.
So if you have a light-squared bishop head to a light-squared corner and if you have a dark-squared bishop head to a dark-squared corner.
If you have a light-squared bishop, the checkmate position looks like this:
The same position would be mirrored for the top-left corner.
This is achieved by the black king being forced to the edge of the board and into a corner, with the king and bishop blocking the enemy king on just 2 squares he can move between - h2+g1 or b8+a7, then the knights move in, 1 knight deleivers check, then the other delivers checkmate. Note how with a light-squared bishop, when checkmate is delivered, ALL the white pieces are on the light squares.
With a dark-squared bishop, the checkmate position looks like this:
Note how with a dark-squared bishop, ALL the white pieces are on dark squares.
The following example shows how to checkmate using 2 knights and a light-squared bishop, with your king aswell of course! I'm showing you with a light-squared bishop because for me, it seems it is the only way I can apply the technique, but I know it can obviously be done with a dark-squared bishop, but when trying to do it over the chessboard, I can only do it with a light-squared bishop. This is not easy to do, when I try and do it I fail much more than I succeed, but that's because I'm not a GrandMaster!! To avoid checkmate, (just like in my previous blog post ) black will try and stay as close to the centre as possible, and avoid the corners like the plague!
The general idea for white is to initially keep the king and bishop close together to block off certain squares, then use the knights to block off other squares, so the enemy king only has 1 or 2 squares he can access, with both of them leading to the edge of the board! It's sort of like a tag-team between the pieces, like an airlock - allowing access to a particular square, cutting off the previous access points, then opening up a controlled route out, then sealing the king in, and repeating this sort of process...
Once the enemy king is on the edge of the board, the h-file (or a-file), then it's relatively simple to force him into the corner and achieve checkmate, the hardest part of this is getting the king to the h-file in the first place, using just minor pieces it is pretty tough... it is an extremely rare occurance to face this ever in real-life, but it's quirky!
This example shows a relative idea of what both sides are trying to achieve. For simplicity reasons, I will show you as white checkmating black, with a light-squared bishop and all pieces on their normal starting squares. I know this is unrepresentative of a real-life situation, which you would seldom face anyway, I feel that this is a good way to show you the ideas behind the technique...