In conclusion, QI believes that this saying was introduced by
Richard Grenier who was attempting to provide a pithy representation
of an idea he ascribed to George Orwell. Later writers and speakers
turned his phrase into a quotation and directly attached it to Orwell.
Over time variants were constructed with modified phrasing.
1) I searched for the quotation. It seems to be pretty doubtful that Churchill said it. And it's hard to see how it is meaningful at all to ask what Churchill meant by the words if he did not actually say them.
2) This page seems to take it for granted that the Churchill of this story refers to his literal writing of history, not to "writing" history in the ...
The quote -- whether correctly attributed or not -- counts as a wisecrack. The speaker implies that "victors write the history" works in both directions: by keeping the log, he could keep the log favorable. Indeed, after the blood has been let the only lasting significance of a battle is what the history books say about it, which is why (for instance) nobody ...