José Rául Capablanca of Cuba, a chess titan of the early 20th century, did not lose a single tournament game from 1916 to 1924, including during the championship match in 1921, when he snatched the title from Emanuel Lasker.

More than a half-century later, Anatoly Karpov, a Russian who was champion from 1975 to 1985, was considered so immune to defeat that the chess world was stunned when he lost to Tony Miles, a British grandmaster, in 1980. (The game was also memorable because Miles played the rare St. George’s Defense — 1 e4 a6. He worried that if he played anything more common, Karpov would have an advantage because of his superior knowledge of the game.)

Magnus Carlsen of Norway, the current world champion, does not have the advantages that Capablanca or Karpov enjoyed.

He closely resembles Karpov in his style of play, and he has a sizable lead in the ratings system used in the world rankings. He wins many more games than he loses.

But Carlsen is not as far ahead of his rivals as Capablanca and Karpov were, in their primes. And when he makes a mistake, Carlsen is more vulnerable than they ever were.

That was how he lost last week to Fabiano Caruana of Italy in Round 4 of the Shamkir 2014 tournament in Shamkir, Azerbaijan, now going on in memory of Vugar Gashimov, an Azerbaijani grandmaster who died in January at age 27.

Carlsen had Black and used the Berlin Defense, which has gained a reputation among elite players as the best way to neutralize White’s advantage after 1 e4.

But Caruana, like Carlsen, plays the Berlin Defense when he is Black. So he knew how to counter it, and he had the patience to probe Carlsen’s position for holes.

Carlsen finally cracked at Move 24. He should have played 24 ... c6. He still would have been in a difficult position, but it would have been one he could defend. Instead, he played 24 ... Kc8, which lost a pawn to 25 Nc7. Carlsen did not play 25 ... Kc7 because 26 e6 Kc6 27 Rd7, threatening 28 Rc7 mate, would have been hopeless. And 26 ... Kb7 27 Rd7 Kc8 28 Rc7 Kd8 29 ef7 Rf8 30 Ra7 Rf7 31 Bd6 (or 31 Bc7) would have gone into a hopeless endgame.

Carlsen fought on and managed to stir up counterplay by threatening Caruana’s king. But Caruana did not have much to worry about. He eliminated the last threat by playing 47 Bg3 to block 47 ... Bg1, leading to 48 ... Bg2, mate.

Carlsen resigned after 53 Ng5 because 53 ... Rf6 54 Rd4 Bc6 55 Rd6 Rd6 56 Nd6 would have been an easy endgame for Caruana.

(New York Times)