Garry Kasparov was born in 1963 in Baku, Azerbaijan, at the time part of the USSR, Soviet Union.
According to the news he has also acquired Croatian citizenship.
In his comeback tournament in the summer of 2017 he still used the Russian flag. However I did see a Croatian flag together with the Russian one on the poster behind him at the signature sessions between the matches.
But why did Garry Kasparov not play under the flag of Azerbaijan?