In his work Theory and History of Historiography (1917), historian and philosopher Benedetto Croce outlines how a true historian, in his view, should study and analyze historical events to conduct an accurate analysis. This process should exclude any fantastical elements and focus solely on the raw realities of historiography. Based on this premise, in the section of his work titled "History of Historiography," Croce, referring to ancient history, explains why classical scholars cannot be considered true historians, as they blended poetry and history. He makes an exception for one figure, whom he regards as the first genuine historian: Thucydides.  

Born in 460 BCE near Athens, Thucydides initially entered politics, supporting the statesman Pericles, and later served as a strategist in the Athenian navy during the war against Sparta in the Aegean Sea. Accused of treason, he chose to leave Athens, spending the next 20 years in Thrace (or possibly remaining in Athens but excluded from political life). During his political exile, Thucydides had the time to organize his extensive writings and compose his magnum opus: The History of the Peloponnesian War. This work meticulously and chronologically examines the conflict between Sparta and Athens, covering the period from 431 to 421 BCE.  

As Croce highlights, Thucydides applies a rigorous critical analysis of both past and contemporary sources (a method resembling that of modern historians), striving to minimize mythological elements while focusing on an exact and detailed description of the military events. Furthermore, Thucydides introduces a cyclical view of history, emphasizing the necessity of understanding the past—through careful examination of sources—to comprehend the present and, ultimately, to anticipate the future where possible.  

By adhering to these principles, the Greek historian laid the foundation for modern historiography: the critical investigation and study of sources, relying on the most truthful accounts to describe the concrete actions of specific events. Thucydides' methods served as a cornerstone for modern historians for many generations.