Can you tell me the country that had participated in the Sydney Olympics with out a national anthem?

Answer 1

It was the East Timor.
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As is customary, Greece, home of the Ancient Olympic Games and birthplace of the Modern Games, led the march, which included 10 500 athletes and 5000 officials from 199 countries. Afterwards, from Albania to Zimbabwe, the nations paraded in English alphabetical order - with two exceptions. Australia, as host nation, was last into the arena, and the tiny East Timor team preceded it.

If any delegations demonstrated superbly the embrace of Olympic goodwill, they were those of East Timor and the two Koreas. East Timor, so recently devastated by civil war, fielded a team without its own flag, without an anthem, without a uniform. There were just four athletes, and they paraded behind a flag bearing the initials IOA (International Olympic Athletes) to a magnificent reception from the crowd.

Answer 2

Uraguay