How did Thucydides reconstruct the speeches in History of the Peloponnesian War?

Thucydides reconstructed the speeches in his History of the Peloponnesian War by writing them in his own words, ensuring they remained appropriate to the specific occasion while adhering as closely as possible to the general sense of what was actually said.1

He acknowledged that it was difficult to arrive at the truth of these speeches, whether he had heard them himself or received reports from others. Despite this challenge, he considered the inclusion of speeches essential to his work, as they allowed him to explain the motives, ambitions, and mindsets of the leading men and states involved in the conflict. By utilizing these speeches, Thucydides aimed to provide a study of human nature in time of war, rather than simply recording events for immediate applause.1