LONDON — It's not much as anniversaries go, but most of us won't be around in 50 years, so we'll have to settle for the 150th anniversary of the start of the American Civil War. The groups who re-enact Civil War battles were therefore out in force on Tuesday, but does it matter to anybody else?

Not much, I hear you cry. But it's still an intriguing question: how different would the world be now if the South had succeeded in seceding from the United States?

As it happens, we have a half-million-word answer to that question: the series of eleven "alternate history" books that American novelist Harry Turtledove has written about a world in which the Confederate States of America successfully won its independence in 1863. It ends up in 1945 with death camps in the CSA and nuclear weapons on Philadelphia and Charleston, and it is fully plausible every step of the way.