50.Qh6+!! Magnus Carlsen retained his world title with one of the most beautiful, stunning moves in the history of the World Chess Championship.

he move was 50.Qh6+!!, and with it Magnus Carlsen retained the title of world chess champion for another two years. Breaking down that notation: It was Carlsen’s 50^th move of the game, and he moved his queen to the h6 square, where it gave check, as indicated by the plus sign. And the two exclamation marks? Those are reserved for a move that is especially brilliant or beautiful. They’re a judgment call, but only the stingiest chess writers will fail to award them here.

50.Qh6+!! is the kind of “mate in two” you see in practice-your-tactics books, where the reader is given a position and told to find a forced checkmate in two moves. The positions are either created from whole cloth for the book or culled from decades of tournament games played by names familiar and not. You can’t be too choosy, since beautiful and unusual mates in two don’t happen often in tournament play.

But this one did. Such moves also happen very rarely in games contested by two top-level players. And they don’t ever happen on the final play in the final game of the World Chess Championship. But this one did.

It had been a frustrating match for Carlsen. He had created nothing of beauty, and he’d also failed to live up to his reputation for slowly grinding opponents into the dust. Indeed, he’d been one-upped by his eely opponent, Russia’s Sergey Karjakin, who’d slipped from his opponent’s grasp repeatedly, drawing the first seven games of the 12-game match from some dubious positions. Carlsen could easily have been up by two or even three games. Instead, the championship was deadlocked.

In Game 8, frustrated at being unable to defeat Karjakin thus far, Carlsen lashed out with a rash and uncharacteristically speculative pawn sacrifice. Fortune did not favor the bold. Karjakin grabbed the pawn and then, after a sloppy exchange of punches and counterpunches, the Russian emerged with a winning endgame that he ably converted.

A heavy favorite to win the match, Carlsen found himself winless and down a point, with just four games left to go. In Game 9, the Norwegian barely dodged disaster, escaping with a fortunate draw after a careless knight retreat allowed Karjakin to unleash a dangerous-looking bishop sacrifice.

In Game 10, Carlsen finally got his first win. It was a slow grind, the kind he’s famous for—not the most entertaining chess to watch, but effective, an illustration of the default style of millennials raised not so much on romantic notions of beautiful checkmates but on the cold assessments of their ubiquitous chess engines. (There are some exceptions to that millennial rule.) Game 11 was drawn with Karjakin as white, and it seemed Carlsen would finally put his Russian opponent away in the final game. He had the white pieces, an advantage roughly equivalent to the serve in tennis, and had won his previous game with white.

But then something curious happened. Instead of aiming for an advantage, Carlsen very quickly played into a drawish variation of the Berlin defense, trading pieces off the board. He was playing for the draw, with white, in the final game, choosing to decide the match in a set of high-stakes, fast-paced tiebreak games. Karjakin naturally acquiesced to the implied draw offer, as he was playing black. Pieces disappeared with astonishing speed: A pair of knights were exchanged on move 7, a pair of rooks on move 11, a pair of bishops on move 18, the other pair of knights on move 19, the queens on move 21, and the other pair of rooks on move 26. It looked like someone had run a vacuum cleaner over the board. Each player was left with just a king, a bishop, and seven pawns, which they shuffled around until move 30—the earliest point at which a draw can be agreed to under the rules of the match. Elapsed time: 35 minutes.

The chess world was astonished that Carlsen had not tried to make the most of his last white and had done so in such a cavalier manner.

In his press conference, Carlsen apologized to fans who were hoping for more of a fight. But he believed he had an advantage in the rapid games, which were played with each side having 25 minutes at the start of the game and 10 seconds added to a player’s clock with each move made. (The players each had 100 minutes for his first 40 moves in the regular games, with 30 seconds added after each move, and 50 minutes added after move 40.) They would play a match of four rapid games, with blitz games (played under even tighter time strictures) to follow if the rapid match ended at 2–2.

The first two rapid games were drawn, with Karjakin making his slipperiest escape yet in the second of the two. The Russian miraculously held a lost endgame that ended in stalemate with Carlsen—who had a king, a bishop, and two pawns—unable to force Karjakin’s king out of the corner.

But instead of rattling Carlsen, this failure only seemed to infuriate him. In the third rapid game, playing black, he sacrificed a pawn to allow his pieces to flood into Karjakin’s position. Under normal time controls this might not have worked, but under rapid conditions Karjakin’s defensive task proved impossible, and he folded under the pressure.

Carlsen had taken the lead for the first time, and all he needed to do was draw the final game, for which he’d have the white pieces.

Needing a win to stay alive, Karjakin abandoned his relatively stodgy openings from earlier in the match. He brought out a Sicilian defense, the most common opening in all of tournament play. It’s a fighting stance, indicating that black has no interest in a draw.

Carlsen chose to meet this with a Maróczy bind formation, which restricts black’s movements severely but, in the variation Carlsen chose, commits white early and is thus not considered very aggressive. But it was a smart idea for this situation: Carlsen needed a draw for the title, and as white the Maróczy bind is relatively easy to play—lots of well-known ideas, lots of shuffling your pieces around without doing any harm. You can just sit on the position, which is ideal for a game with fast time controls in which you only need to draw.

It worked: Karjakin got behind on time and flailed about looking for counterplay, but the bind proved strong. He lost a rook for a bishop and was down to playing only on the increment—the 10 seconds added to the clock after each move—as he searched for a miracle strike against the white king.

And then, it looked like he might have found it. In a sudden sequence of moves, Carlsen’s army of pieces seemed to abandon his own king completely. One of his rooks chased Karjakin’s king off the back rank to the edge of the board, but in the meantime Karjakin’s rook and queen had pinned Carlsen’s king into the corner. Karjakin threatened no less than four checkmates, and there’s no way Carlsen could have sidestepped them all. The only problem for the Russian: It was Carlsen’s move.

For a moment—at least if you were following the match without the aid of chess engines, which can tell you the best move in real time—you might have thought Karjakin had pulled another Houdini. Carlsen had no way to stop all of Karjakin’s many threatened mates against his own king and only two possible checks himself, one a nonsensical rook check, the other a nonsensical-looking queen move that simply gave her majesty away for nothing—in fact, she could be captured in two different ways, by either a pawn or by the king itself.

What makes a chess move unexpected? That an experienced player rejects it intuitively since it does not fit the usual patterns. A grandmaster does not find the best move in a position via brute force, as a computer does. Instead, he or she recognizes patterns of placement and movement among clusters of pieces, rejecting the vast majority of moves intuitively.

50.Qh6+!! is a move that even a great mind could be forgiven for missing, especially since Carlsen had to foresee it several moves earlier, when he made the decision to abandon his king to Karjakin’s invading rook and queen.

Carlsen’s queen move, pictured above, looks at first glance like the world’s worst kamikaze attack: His queen did not capture anything and could itself be captured in two distinct ways. But there was a method to this madness: Both of the moves Karjakin could make to capture Carlsen’s queen would lead to a checkmate for the Norwegian.

Option 1: If Karjakin’s king captures the queen, then he has been lured away from his hidey-hole and the rook on c8 delivers mate at h8.

Karjakin could only choose which rook would be his executioner, and he decided on neither, resigning the game instead.

The two potential moves above look quite different from each other and represent somewhat unusual mating patterns, making them easy for the pattern recognition part of a grandmaster’s brain to miss. But Carlsen isn’t a typical grandmaster. With this beautiful coda, a move that will appear in a hundred future tactics books, he redeemed what had been a rather lackluster and disappointing championship match.

50.Qh6+!! also had a poetic touch: On his 26^th birthday, Carlsen won the world championship by moving his queen two squares to the sixth rank. Not a bad gift for himself and for everyone who loves chess.