Teribus, good to read that you enter the discussion. Let me start with your last point, most important to me: a "grateful nation", or any other feeling held by a "nation", is simply no longer a view adequate to the world of today. Those who indulge in such emotions are easy to exploit for nationalist agendas. (Sports events have been invented to canalize the desire for collective emotions, with considerable success, but sometimes of counterproductive effect.)—

Who decides what constitutes "Fair"?

A good question. I hope one day the UN Security Council will be replaced by a tribunal similar to the Hague Tribunal, to do it authoritatively. Until then, and well afterwards, the notion of a fair and acceptable peace is similar to the one of "good music": we cannot say how exactly to compose it, but often we know it when we hear it. In other words, it is an art. Actually it is as old as humankind; anthropologists say that the invention of language (= symbolic communication) was not so much an intellectual or physiological problem, but one of trusting each other's word - to a certain extent. The extent became larger and larger; now it simply has to extend beyond national borders. The main reason is our "globalized" society and economy. The second reason is the existence of weapons of mass destruction. The third one is the presence of mass media which can produce synchronized emotions in large groups in a very short time, compared to, say, the crusades of the Middle Ages. WWI symbolizes the disastrous potential of this era, and must therefore not be remembered as any kind of victory for anyone.

Of the details of diplomacy before 1911, the following seem important to me:

1. France and Britain considered Germany a threat on a worldwide scale, i.o.w. a rival for ruling the waves and colonies. Belgium was not an object of the war, it was important only as a pawn in the propaganda game. The scenarios were prepared long before 1914 and the war crimes of German troops in Belgium.
2. Polititians, monarchs, and newspaper editors publicly fueled outrage on the other side, respectively, depriving peace advocates of good arguments against their "hawks".

The second effect is particularly relevant today. The current Iran affair is much more difficult to treat, but success now seems possible. Sanctions and military threat are necessary instruments, legitimate and efficient if used in a context of fair peace offers, as mentioned above: fair also in the eyes of reasonably-minded Iranians. Needless to say that the tackling of the Iran crises was and is far from perfect; I use this example to demonstrate that war is rarely the only option.