Sosonko emigrated in 1972 from the Soviet Union in the Netherlands. In 1973, he won the championship of the Netherlands. In 1974 he became an International Master in 1976 grandmasters. In 1978 he was again champion of the Netherlands. He still won in many other international tournaments, such as 1976 in Lugano, 1977 in Wijk aan Zee, 1978 in Nijmegen, 1981 in Wijk aan Zee, 1993 in Polanica -Zdrój.
Sosonko often played in the Dutch national team, including at 11 Chess Olympiads. He scored a total of 60 points from 96 games (28 wins, 4 losses, 64 draws).
1981 signed him to the club king Springer Frankfurt for the top board in the Chess League.
In 2001 he wrote Russian Silhouettes (ISBN 90-5691-078-7 ), as sequels released in 2003 The reliable past (ISBN 90-5691-114-7 ), 2006 smart chip from St. Petersburg ( ISBN 90-5691-169-4 ) and 2013 The World Champions I Knew (ISBN 978-90-5691-418-9 ). The books contain biographical essays on some famous, some less well-known chess master who knew Sosonko personally. They are an interesting source about the internals of the Soviet chess school. Sosonko was awarded the 2004 title FIDE Senior Trainer.
His best historical Elo rating was 2693 This he reached in October 1982 His current Elo rating is 2525 (as of November 2010).. .