Leaked: World Championship preparation comes to light

by André Schulz
11/11/2026 – Opening preparation for a World Championship match was recently published on X. Gukesh and Sindarov need not worry, however. The whistleblower is Peter Heine Nielsen (pictured), and the secrets he revealed are already 15 years old. And then even older preparation came to light...

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World Championship preparation leaked

Peter Heine Nielsen is probably the most successful second in recent chess history. He currently works for Magnus Carlsen and helped the 16th world champion during several successful title defences. Before that, Nielsen worked for Carlsen's predecessor, the 15th world champion Viswanathan Anand.

Nielsen has also helped ChessBase in the past. During Deep Fritz's match against Vladimir Kramnik in Bonn in 2006, he adapted Deep Fritz's opening book specifically for the match against Kramnik and determined which variations Deep Fritz should use in response to Kramnik's openings - successfully, as we now know.

Recently, the strongest Danish player since Bent Larsen posted a photo on X showing the screen of his old laptop, on which Anand's preparation for the World Championship match against Veselin Topalov can be seen. The photo only shows a ChessBase list of variation trees rather than the trees themselves. Even so, a few names can be made out. In response to a question, Nielsen even showed one of the variations in the post.

The start of the World Championship match in Sofia was hardly auspicious. The match was due to begin on 23 April 2010, but on 14 April a new explosive phase of the Eyjafjallajökull volcanic eruption began in Iceland, and before long air traffic over large parts of Europe was suspended for safety reasons because of the spreading ash cloud. Anand and his team were unable to travel by plane as planned and instead had to hire a minibus, in which they made the long journey from Bad Soden to Sofia.

In his post on X, Peter Heine Nielsen described how the team used the long journey to go over their prepared variations once again. Nielsen read the moves aloud from his laptop. Anand, Rustam Kasimdzhanov, Surya Shekhar Ganguly and Radosław Wojtaszek followed the variations blindfold and discussed their advantages and disadvantages.

Because of the difficult travel conditions, FIDE granted a one-day postponement. Anand lost the opening game on 24 April, but immediately levelled the score in the next game. In the end, he won the match and retained his title.

Photo: ChessBase.in

The decisive game:

When staff at the Euwe Centre in Amsterdam saw this "leak" from Peter Heine Nielsen, they did not want to be outdone and followed up with a "leak" from their own archives: Max Euwe's preparation for his 1935 World Championship match against Alexander Alekhine.

There were no computers or ChessBase at the time, of course, but the opening preparation followed the same principle. Euwe's notes also consisted of lists and variation tables, in this case handwritten on index cards, perhaps not quite as extensive as Anand's.

Max Euwe's official second for the match was Géza Maróczy. Salo Flohr and Ernst Grünfeld also helped with the opening preparation. The latter had an extensive opening card index. Euwe won the World Championship match against Alekhine. Two years later, however, he lost the return match.

Photo: Dutch National Archive

The decisive game:


Experts examine the games of Max Euwe. Let them show you which openings Euwe chose to play, where his strength in middlegames were, which tactical abilities he had or how he outplayed his opponents in the endgame.
Max Euwe became the fifth World Chess Champion after beating Alexander Alekhine in the 1935 World Championship match. A maths teacher by profession, Euwe remained an amateur throughout his life, but was still the best chess player in the Netherlands, and one of the world's best players. Euwe holds the record for the most Dutch national championships, with twelve. After winning the World Championship, Euwe was also the world's best player for a while. He lost the title again in 1937 in the rematch against Alexander Alekhine.
Free video sample: Openings



André Schulz started working for ChessBase in 1991 and is an editor of ChessBase News.
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