I grew up hearing his descriptions on every conceivable historical event, and I was amazed of how much he seemed to know about everything. At the time I felt that he was truly knowledgeable, and I couldn't even conceive of knowing even a fraction of what he knew.
Then, when I grew older, I finally asked how he managed to know so much. His response? Laughingly, he told me that he made a lot of educated guesses on how things seemed to him!
That was a decisive formative experience for me: so that's how he pulled it off? Now I'm much more relaxed with the degree of detail I can know about things, and I also take what anyone is saying at any one moment with a saltier dose of skepticism. We're all humans after all, and telling tales is deeply rooted in our natures.
He is a history buff, though, knowing "everything" about every king and fight the last centuries in Europe. So I think what he told would be plausible and rooted in truth. But makes me wonder about the stories he told me as a kid, before smart phones that could rebuff his tales.