As others have pointed out, the "battle" is actually against both usage 1 and 2: the original meaning[1] is to kill only 10% of a legion (etc) as punishment for

As others have pointed out, the "battle" is actually against both usage 1 and 2: the original meaning[1] is to kill only 10% of a legion (etc) as punishment for some misdeed. It's the large reduction implied in current usage of decimate that gets pedants all riled up. [1]: https://en.wiktionary.org/wiki/decimate#Etymology https://en.wiktionary.org/wiki/decimate#Etymology