> or did everyone make it up?

Essentially they did. It was an expression of strained optimism, not propaganda.

And it was partly based on the expectation - made vivid by the Second Balkan War of 1913, which had resulted in 160,000 casualties - that a general war would soon become unendurable for both sides.

The war in the Balkans, widely reported in the papers, had lasted less than six weeks.