History has many uses, but not all of them are that useful. This one is downright annoying (as you probably guessed from the title). I'm reading Tom Holt's Overtime at the moment, which is a funny, well thought out book containing time travel, the fundamental interconnectedness of all red tape, medieval poets conducting world tours, evil henchmen put in for repairs between scenes... you know, the usual.
It also features a number of references to the Third Crusade. You know, the one everyone's heard of, with Richard the Lionheart, Philip Augustus, bouts of being kidnapped in Germany and so on. It's in the background of assorted versions of Robin Hood. At least, I think it's the Third Crusade, and so do the reference sources I checked. Tom Holt seems to be insisting that it was the Second.
You have no idea how much that annoys me. Calling the Third Crusade the Second not only means that the nice line of medieval french kings with crusades (Louis VI, Louis VII, Philip II) gets disrupted, it also effectively ignores one of the most wonderfully incompetant attempts at a crusade ever put together. Running from 1147-49, with Bernard of Clairvaux preaching it and Louis VII of France putting his not inconsiderable weight behind it, it should have been a roaring success... except that no one seemed to know what they were doing on the military side of things. The result was a largely humiliating defeat that I find rather amusing (look, after years of following the England cricket team you get a skewed view of failure).
As far as I can see, one of three things has happened. One, Holt has followed a book that has somehow decided the second crusade didn't really count. The numbering of crusades was a bit random for several years, so it's possible. Two, he hasn't done any research, deciding to rely on what he already "knew". Well sorry, but it's the sort of thing you'd expect someone to check (actually, why don't publishers have special "Crusade Number Checking Editors"? It would save a lot of trouble).
The third possibility is that I simply haven't read far enough into the book yet. There's time travel floating around, so I suppose the order of things could get changed yet. I hope so. History can be fun (I'm told), but there are moments when it can spoil an otherwise lovely book.