This particular quote, from an omnipotent narrator's perspective, has always concerned me:
... War awoke the tranquil nation’s appetite for bloodshed. ...
Essentially, Noxus invades Ionia, and demonstrates how much their peaceful ways really put them at a disadvantage. The specialist schools who practiced the martial arts certainly held their own - as highly trained specialists are wont to do - but the citizenry at large was essentially gunned down by the hundreds. It makes sense to me why the cultural shock of this might swing the Ionians to the opposite spectrum (peaceful isolationists to crusaders). It also makes sense to me, however, that this might strengthen Ionia's resolve to stay to its ways.
The martial schools already exist, they're just (seemingly) underpopulated. There would be an immense influx of people who want to protect their families, villages, and nation at large. To infer through subtext that a fundamental shift in Ionia would essentially put them closer to Noxus and Demacia strikes me as ... distasteful.
I could be misreading the whole foreshadowing, though. I've seen this line of story telling done before and it just always white washes the intricacies of being peaceful in the face of war mongers.