The Blunder that Made Magnus Carlsen the World Chess Champion

Game 9 of the 2013 WCC

The 2013 World Chess Championship was held in Chennai, India between the defending champion Viswanathan Anand and the challenger Magnus Carlsen. After 8 games of play, Carlsen was leading 5-3, and only 4 games remained. In game 9, Anand had the white pieces and was pressing for a win. Both sides played aggressively, grabbing space on opposite sides of the board in what would result in a closed position in the center and kingside. After 27 moves of perfect play from both sides, this critical position was reached.

Yes, in case you are wondering, Carlsen did promote to a second queen, giving check. Before this move, White intentionally played Rf4! to try and swing the rook over to h4 to deliver mate. After b1Q+, what is the best move for white, and can you find the continuation that will result in an equal endgame?

White's Options

Moving the king does not make any sense, as black will continue to check and improve the Queen's position. Rf1 makes even less sense as Anand intentionally allowed the promotion of the queen to go for Rh4. Hence we are down to two moves, Nf1 and Bf1. However, only one moves draws; the other loses.

Congratulations if you found Bf1, the only drawing move. Before we get into this drawing line, let's look at what Anand played.

The Blunder of the Championship

If Anand had played Bf1, the game would have likely ended in a draw, but at least he wouldn't have lost the game. Anand went for Nf1?? and completely overlooked Carlsen's reply. Can you find it?

Black to play and win.

Carlsen was able to find the winning move Qe1!! This completely stops Rh4 and then Black would sac the queen for it, and emerge up an entire rook. Remember, Black is currently up an entire queen, so sacrificing the queen for the rook enables Carlsen to be up a rook in the end. Anand just resigned after Qe1, essentially ending the World Championship right there (they did play a 10th game, but that ended in a draw).

What was the idea behind Nf1?

Anand saw Bf1 and saw Black's reply as Qd1!, ready to interpose via h5. However, Anand thought if Nf1 Qd1 Rh4 Qh5 Rxh5 gxh5 Ne3 he is winning (which he is), as d5 is undefendable. If Bb7 then Nf5 would be deadly.
As a result, he quickly played Nf1, but simply overlooked the more powerful Qe1, ending the plan in its tracks.

Why is Bf1 drawing?

After the only move Bf1, black's reply is also an only move? Can you spot it?

Yes, Qd1! is the only move, meeting Rh4 with Qh5. After Nxh5 gxh5 Rxh5 Bf5 black has defended against the mate threat and is technically up a piece for two pawns.

However, one such line for Anand is g6! Bxg6 (otherwise you get mated) Rg5 Nxf6 gxf6 Qxf6 Rxd5 Qf3 Rc5 Qxc3 and Rxc4.
After the dust has settled, everything has blown up and with equal material, the game should end in a draw. Despite Anand's aggressive play, Magnus was able to defend excellently with only moves, and one fatal blunder by Anand cost him the entire World Championship. Of course, Carlsen would go on to dominate until Ding became the World Champion in 2023.

Conclusion

That's all for this game and interesting puzzle on how Magnus Carlsen became the World Champion.