No word for sex

I remember reading a science fiction novel in which a story was recounted by one character to another of a "first contact" expedition to a world. The members of the expedition had been assured that the inhabitants were peaceful because they had no word for war.

When they landed, they were slaughtered.

True, the inhabitants had no word for "war" - that's not sufficiently refined. They had words for

* war because of land conflict

* war because of water rights

* war because of ancient insult

* genocide as retribution

and so on.

But no word for "war".

I can't remember the novel - perhaps some of you can. If not, I just might have to re-read my collection to find it.