How big a war?" "A worse one than the one fifty years ago, I expect," said Cheery. "I don't recall people talking about that one," said Vimes. "Most humans didn't know about it," said Cheery. "It mostly took place underground. Undermining passages and digging invasion tunnels and so on. Perhaps a few houses fell into mysterious holes and people didn't get their coal, but that was about it." "You mean dwarfs just try to collapse mines on other dwarfs?" "Oh, yes." "I thought you were all law-abiding?" "Oh, yes, sir. Very law-abiding. Just not very merciful.