In plain words, ours
I lived through all of it, old enough to understand it. I was exiled for twenty years after my command at Amphipolis, which let me watch both sides closely.
I lived through the whole of it, being of an age to comprehend events, and giving my attention to them in order to know the exact truth about them. It was also my fate to be an exile from my country for twenty years after my command at Amphipolis; and being present with both parties, and more especially with the Peloponnesians by reason of my exile, I had leisure to observe affairs somewhat particularly.
Thucydides, History of the Peloponnesian War 5.26.5Translated by Richard Crawley (1874)Read the full passage (Thucydides, History of the Peloponnesian War 5.26.5, opens scaife.perseus.org)