Although the Great War as "1914-1918" was not a major issue military for Greece, it forms part of a 10 year war that made the current version of Greek nationhood a reality. The country doubled in size compared to 1912 and obtained a slightly more diversified economy with the addition of the North, rather than just olives and blackcurrants as in the 19th century. OTOH, it led to the absurd and disastrous adventure of the Asia Minor campaign of 1920-22 which ended with at least 1 million Greeks (and at least a quarter of a million Turks) being forcibly torn from their homes of centuries. My own family on my mother's side is of this refugee origin, so I wouldn't exist without the Great War

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The "Catastrophe" of 1922, as it's still called, is the central event of modern Greek (post-Ottoman) history. It accentuated the political divisions of 1914-20 between supporters of Venizelos and Royalists, and directly caused the social scars that led to the disastrous Civil War of 1946-9. It still casts a shadow over the relations between Greece and Turkey, two countries which should be the closest friends instead of the silly third world rivals they are now.
I find it amazing that WW2 gets so much more attention in the popular mind, whereas the first war was so much more fundamental. Most people basically think of it as men stuck in holes in the ground and being miserable for no good reason, whereas it was the cataclysmic watershed between 19th century civilisation and the world we know now.