It was Greece's most disastrous military gamble that led to massacre and defeat, leaving an open wound in relations with Turkey that festers to this day.

"A hundred years ago, the body of our nation lost a precious part," Prime Minister Kyriakos Mitsotakis said this weekend as the country prepared to mark the Asia Minor Disaster — a trauma so raw many simply call it the "Catastrophe".

As the Ottoman Empire crumbled at the end of World War I, the Greek army took parts of Anatolia that the Byzantines had lost to the Turks 500 years before.

But by 1922, Ataturk — the founder of modern Turkey — reversed the tide in a stunning counterattack.

The Greek army's frantic retreat ended with the burning of the coastal metropolis of Izmir — Smyrna to the Greeks — and the massacre of its inhabitants. The prosperous Greek community that had lived there for centuries had to flee for their lives.

Greece and Turkey later signed the Treaty of Lausanne to set new borders and carry out the world's first mass population exchange.

So great was the upheaval that in 1928 a fifth of Greece's population were registered refugees, some 1.22 million people.

Up to 400,000 Muslims from Greece were sent the other way.

Greece forever changed

The Anatolian refugees — who included the young tycoon-to-be Aristotle Onassis — changed Greece forever, argued historian Giannis Glavinas, bringing their business acumen, progressive ideas, rembetiko folk music, and Anatolian cuisine with them.

"After 1922, Greece is no longer the same," said Glavinas, who has curated a commemorative exhibition at Technopolis, the city of Athens industrial museum.

To keep memories alive, the Christian refugees from Asia Minor often gave their new settlements in Greece the names of their old hometowns, adding the prefix "nea" for "new", such as Nea Smyrni or Nea Filadelfia.

"The stories of our grandparents from Asia Minor, the memories of their lost paradise, were our lullabies," said Roula Chatzigeorgiou, head of the Museum of Hellenism in Asia Minor in Nea Filadelfia, now an Athens suburb.

"The wound remains open," said Roula, whose grandmother fled the killing and destruction with eight children in tow.

So much so that the Greek parliament will also hold a special session dedicated to the tragedy on Wednesday, the official remembrance day for the Asia Minor Disaster.

Across the Aegean Sea in Turkey, the same momentous events are cause for celebration, marked by Armed Forces Day on 30 August that hails the creation of modern Turkey.

This year, Turkey's President Recep Tayyip Erdogan has repeatedly hammered at Greece's painful defeat in speeches designed to shore up support ahead of a difficult re-election bid next year.

Athens formally complained to the EU, NATO, and the UN last week after Erdogan warned in a speech: "We have one thing to say to Greece: Remember Izmir."

With Erdogan and his officials questioning the sovereignty of some of Greece's Aegean islands as well as the Lausanne Treaty, Greco-Turkish relations are at their lowest point in three decades.

Rena Zalma, 74, whose family once lived in Anatolia, said Erdogan's words "can only cause sadness among the descendants of refugees and stir up hatred between peoples who lived well together.

"Tensions are fueled by leaders. But the people understand and respect each other," she said.

'Seeds of Turks'

Landing in a country shattered by war and defeat, the Anatolian refugees were ostracized by their fellow Greeks, sheltering in shanty towns on the outskirts of Athens, Piraeus, and Thessaloniki and other cities for decades.

Despina Mogogiannis said her refugee mother and grandmother met with an "icy" welcome in Athens.

"We have always been perceived as the 'seed of Turks' in whom mainland Greeks could not have complete confidence," the 72-year-old told AFP.

Her grandmother, whose husband was killed and whose six-month-old daughter died on the journey to Greece, "always believed that she would return home. She kept the key to her house until her death," said Mogogiannis, fighting back tears.

"This story has troubled me all my life, my children too. Four generations have borne the weight of this tragedy," she added.