IM Kiprian Berbatov first played a FIDE rated tournament when he was 9 years old, competing in the 1st Sofia Open in July 2006, scoring at least 4 points in 9 rounds. Also in 2006, he played in the World Youth Championship (U10) scoring 7/11 and placing =12th and scored his first tournament win in the 14th Memorial Nikola Baharov in Sofia, scoring 6/6 in a field whose average ELO was 2315, in effect a category 3 tournament, including a win against IM Kalin Karakehajov and Krasimir Rusev (then rated 2453). Not shying away from difficult competition, the 12 year old competed in the 29th Bulgarian Open Championship "Georgi Tringov" 2007, scoring 5/9.
He participated in numerous international tournaments in 2007, one of the best results being =3rd in the International Tournament in Torredembarra in 2007 scoring 6.5/9, half a point behind the two joint leaders. In April 2008 during the European Championship, aged 11, he scored his first win against a GM, Julian Radulski. The September quarter of 2008 was especially active and productive for Berbatov, competing in 8 international tournaments and picking up 96 ELO for his efforts, to take him to 2346 3 months after his 12th birthday; his best effort in this period was =1st in the VIII International Alonso Leira Memorial Tournament shortly after his 12th birthday. In September 2008, he won the European U12 championship.
Berbatov's successes continued into 2009, and he was awarded the IM title in this period, aged 12. He scored 6/9, one point off the lead, in San Sebastian, and came =1st with 7.5/9 at the Vila Torredembarra International Open, his only loss being to joint first placegetter GM Krasimir Rusev. In October 2009, he was =1st (2nd on count back) at the International Open at Rohde in France, with 7.0/9 and won the Roquetas de Ma International Open, with 7.5/9. He came =1st (4th on count back) in the International Open at Seville in January 2010.
Berbatov's subsequent form since then was comparatively patchy, although he scored a strong 5/7 result in the Spanish First Division Championships. He played first reserve for Bulgaria in the Chess Olympiad (2010), scoring 4.5/8 with a 2457 performance rating. He also played in the World U14 championships but scored only 7/11. 2011 started well with an outright win in the 75th Bulgarian Individual Chess Championship Semifinal - Men, scoring 7.5/9 with a performance rating of 2627. Although he was unplaced in the Reykjavik Open (2011), his 6/9 result (TPR of 2565) was a point off the lead, and included a win against co-leader Jon Ludvig Hammer, and draws against co-leaders Yuri Aleksandrovich Kuzubov and Vladimir Olegovich Baklan. His patchy form continued in the 12th European Individual Championship (2011) where he scored 6/11, a TPR of 2382 reflected in the fact that he lost to the four of the five GMs he faced in the event, but nevertheless managing to defeat Victor Markovich Mikhalevski. Soon afterwards, he returned some modest results in the French and Bulgarian team championships, followed by some equally modest results in the 3rd International Tournament in Albena, Bulgaria (6.5/9) and in the Varna Open (also 6.5/9) before an upbeat result in the 2nd Festival de Vaujany in France, in which he placed outright 2nd, half a point behind powerful Romanian GM Andrei Istratescu. He also participated in the 5th International Tournament in San Juan, playing at rating strength and scoring 6/9, but scored only 5.5/9 in the European U16 Championship in September 2011, losing three games to much lower rated players.
In November 2011 and at the age of 15, Berbatov announced his retirement from chess to concentrate on mathematics.*
Wikipedia article: Kiprian Berbatov