In Life on the Mississippi there is a queer little illustration of the central weakness of Mark Twain’s character. In the earlier part of this mainly autobiographical book the dates have been altered. Mark Twain describes his adventures as a Mississippi pilot as though he had been a boy of about seventeen at the time, whereas in fact he was a young man of nearly thirty. There is a reason for this. The same part of the book describes his exploits in the Civil War, which were distinctly inglorious. Moreover, Mark Twain started by fighting, if he can be said to have fought, on the Southern side, and then changed his allegiance before the war was over. This kind of behaviour is more excusable in a boy than in a man, whence the adjustment of the dates. It is also clear enough, however, that he changed sides because he saw that the North was going to win; and this tendency to side with the stronger whenever possible, to believe that might must be right, is apparent throughout his career.
Orwell is quite wrong about this. Mark Twain was 22 when he began studying to be a pilot on the Mississippi and 24 when he got his license. By the age of 25 he had already abandoned the Confederate Army had headed west to Nevada. 25 strikes me as still being pretty young. Its also very odd for Orwell to claim that Twain was jumping onto the winning team. It looked like the Confederacy was going to win the war or at least force a negotiated peace well in to 1864, a good three years after the young Sam Clemens had headed west.
Childhood heroes let you down as you get older, but that's sort of their job and Orwell is no different. Unfortunately he couldn't resist fitting his facts around his theories, a flaw that shines through some of his work. However when he was good he was very, very good. Take a look at England Your England or Such Such Were The Joys as nice examples of his high art.