Thucydides was an Ancient Greek historian and general from Athens. He lived from about 460 BC to 400 BC. Thucydides is known as the father of scientific history and of political realism, especially in the study of international relations theory. His main work is History of the Peloponnesian War, which details the war between Sparta and Athens that was fought during Thucydides' lifetime.
In English, the correct pronunciation of Thucydides is Thoo-sihd-ih-deez. To pronounce Thucydides the right way, first of all, the "th" is pronounced like in the word "though". Second, the "u" is pronounced with an "oo" sound. Then, in the second syllable, the "c" is pronounced like an "s", while the "y" is pronounced with a short "i", that is to say an "ih" sound, exactly like the "i" in the third syllable. In the last syllable, the "e" is a long "e", so it is pronounced like the "ee" in the word "seen".