Throughout the years participants in the Olympics have come from many countries. However, not all countries have participated. This may be due to the country voluntarily not sending athletes to the country. Other reasons include that their own country through their national Olympic committee forbid them to represent their country in the Olympics. After the major wars, those countries that lost the war were punished and were not allowed to send athletes to the Olympics to represent these countries.
This includes Germany, Turkey, and Japan plus a few more. Syria is not on the list of a country that has been banned from the Olympics. However, Syria may not allow itself to send representatives due to the problems in the country.