In The Hydrogen Sonata, by Iain M Banks, he mentions an all out Galactic war by the Culture within living memory.
It seemed perverse to some, but for all their apparent militarism the Gzilt had remained peaceful over many millennia; it was the avowedly peaceful Culture that had, within living memory, taken part in an all-out galactic war against another civilisation.
Which war is this? The book takes place 500 years after Excession, and the Idiran war was long before that...