He continued to play in Europe and around the world to an advanced age, living in his adopted country of Switzerland. He frequently represented their
Olympiad team on top board, beginning in 1978, even though his
Elo rating was sometimes considerably below that of compatriot
Vadim Milov, who appeared not to make himself available for selection. From 2001 onwards, Korchnoi became a prolific author of books on his career, publishing five new volumes, including two books of annotated games, an updated autobiography, and an overview (along with several other authors) of Soviet politics applying to chess; he also wrote a book on rook endings. In 2001, Korchnoi won the
Biel Chess Festival for the second time in the grandmasters division, having also won in 1979. This 22-year gap still stands as the longest time period between being champion at Biel tournament, or quite possibly any international chess tournament. In September 2006, Korchnoi won the 16th
World Senior Chess Championship, held in
Arvier (Valle d'Aosta, Italy), at age 75, with a 9–2 score. Korchnoi scored 7½–½ in his first eight games, then drew his last three games. Korchnoi was ranked number 85 in the world at age 75, the oldest player ever to be ranked in the FIDE top 100. The second-oldest player on the January 2007 list was
Alexander Beliavsky, age 53, who was 22 years younger than Korchnoi. In 2011, Korchnoi was still active in the chess world with a notable win (in
Gibraltar) with black against the 18-year-old
Fabiano Caruana, who was rated above 2700 and 61 years Korchnoi's junior. Korchnoi became the oldest player ever to win a national championship, when he won the 2009
Swiss championship at age 78. He won the national title again a few months after his 80th birthday in July 2011 after a playoff game with
Joseph Gallagher.
Declining health Till the very end, Korchnoi remained a fierce competitor. In late December 2012, it was reported that Korchnoi was recovering from a stroke and was unlikely to play competitive chess again. He was scheduled to play in the 37th
Zurich Christmas Open tournament in December 2013, but he withdrew for health reasons. However, in 2014, he returned to the board to play a two-game match against GM
Wolfgang Uhlmann (1935–2020), winning both games; the combined age of the two players was 162 years, which is almost certainly a record for a standard play match between Grandmasters. In 2015, the two played a four-game rapid match (25 minutes per player for all moves, plus 30 seconds extra per move), which was drawn 2–2. Korchnoi's final match against another Grandmaster was a similar four-game rapid match in November 2015, against GM
Mark Taimanov (1926–2016) – the first time since 1980 that Korchnoi had played in an official or friendly match against an opponent older than himself. The combined ages of the players was 174. Korchnoi won the match 2–1 with one draw. ==Death==