Five Lessons From Hikaru's Hardest Checkmate

Are you one of the hundreds of thousands of people who have watched a video of GM Hikaru Nakamura's most difficult checkmate? Here's one of several versions around the web.

Nakamura reaches an endgame where he only has two knights, and he's still able to deliver mate in a blitz game against a GM-strength opponent. How did he do it, and what can we learn from this ending? Let's dive in.

1. What is the Troitsky Line?
2. You Don't Need to be Perfect
3. Corner The King
4. Push Your Pawns
5. Leave Yourself Time For The Endgame

1. What is the Troitsky Line?

GM Edmar Mednis claimed that two knights being unable to force checkmate against a lone king is "one of the great injustices of chess." The knights can't do it because it would require stalemating the opposing king along the way. If the opponent still has one pawn, however, there are positions where the stronger side can let that pawn advance, avoid stalemate at the right moment, and win the game. More than a century ago, Alexey Troitsky worked out how far advanced each pawn could be for the stronger side to still force checkmate.

Knowing about the Troitsky Line, if you're playing with the white pieces against Nakamura, which pawn would you advance?

Notice that White advanced the wrong pawn to start, but Nakamura blockaded the white pawns incorrectly, allowing White to secure a drawn position again. This brings us to our next lesson.

2. You Don't Need To Be Perfect

Two of the best players in the world made critical mistakes in the position above. It happened again just three moves later, when White allowed Black a chance to win, and Black wasn't able to take advantage. Once again, Nakamura's error, 69...Kxh3, could have been avoided by thinking about the Troitsky line. The winning plan involves keeping the white pawn that's behind the Troitsky line on the board.

Despite multiple errors in this endgame, Nakamura still managed to win. That's because the defending side has a difficult task as well. If you focus on cornering the opposing king, there's a good chance that you'll be able to win, even in positions that could be held with perfect defense.

3. Corner The King

Did you see the end of the main line above? The fastest win involves giving up a knight and reaching a rare position where one knight can checkmate against a king and pawn.

The one-knight mate is a rare opportunity, but even in the actual game, Nakamura made progress toward checkmate by using his king and one knight to push White's king. Meanwhile, the other knight sat in front of White's final pawn, preventing it from advancing. In the position below, White should still be able to defend, but Nakamura has made considerable progress by pushing his opponent's king toward the bottom left corner of the board.

4. Push Your Pawns

While both sides made several errors in the endgame, White made one repeated mistake that he must have regretted later. He had several opportunities to advance his last pawn. If Black had captured that pawn, the game would have ended in a draw, but the alternative would have been allowing it to promote. 

Although White can still draw at the end of the sequence above, he still had to find some good moves in the closing seconds of the game. If he had advanced his pawn when he had the chance, Black would never even have had an opportunity to threaten checkmate.

5. Leave Yourself Time For The Endgame

With all of the themes above, the most important may be that you need to give yourself a chance to think. By the end of the game, White was premoving his moves, and that is what caused the decisive error at the end of the game.

White willingly moved his king into the corner, but if it had gone the other way, then Black would have had nothing more than a draw. White was a strong player and would have seen this forced checkmate if he had some time to think, but he premoved instead. Maybe the most universal lesson from this game is that you need to give yourself time to think in the endgame. Even the best of us will make mistakes with no time on the clock.

Here's the whole messy, impressive, wild game.

What was the most complicated ending that you've ever played? Let us know in the comments.