[Spoilers] Old Harry's Game

[Old Harry]

The odds that the attacker will win each round is given by A/(A+D), so the odds the defender wins a round is D/(A+D).

(A & D represent the strengtht of attacker and defender)

And here's the full article: Combat Explained

(it's actually quite good)

Ah, that explains it - thanks!

BaII - I think the jump points are because if you get hit for 25 points it only takes four hits to kill you while if you get hit for 24 points it takes five hits to kill you (which is much less likely). Although perhaps this has an effect too...