Computer chess programs are so popular, and so good, that almost anybody can use one to figure out where a player went wrong  when the game is over. But at the board, competitors can rely only on their brains and wits (unless they are cheating) and are bound to make mistakes, especially when they are under pressure.

One reason why Veselin Topalov of Bulgaria is so good is that he forces opponents to make mistakes. Ranked No. 2 in the world, he is an aggressive player who is always trying to attack. There are problems with this approach, when being aggressive is not justified. But the constant pressure that he places on his opponents often causes them to crack, even when Topalov himself has made a mistake.

His style was on display at the annual elite tournament in Linares, Spain, which ended on Wednesday. Topalov edged the defending champion, Alexander Grischuk of Russia. Topalov beat Grischuk in Round 5, though with the benefit of computer-aided hindsight, he probably should have lost.