After Greek fighters took Livadeia on 1 April 1821, the Ottoman commander Hursid Pasha dispatched two of his most capable commanders from Thessaly — Omer Vrioni and Köse Mehmed — at the head of 8,000 soldiers. Their orders were to crush the revolt in Roumeli and then proceed to the Peloponnese. Diakos and his forces, joined by fighters under Dimitrios Panourgias and Yiannis Dyovouniotis, moved to block the Ottoman advance near Thermopylae. They divided their 1,500 men across three defensive positions: Dyovouniotis at the Gorgopotamos bridge, Panourgias at the heights of Halkomata, and Diakos at the bridge over the Alamana stream, south of Lamia.

The plan required all three positions to hold. None of them did — but not for lack of trying.

Setting out from their camp at Lianokladi, the Ottoman forces divided as they approached. The main column struck Diakos's position while the other engaged Dyovouniotis, who was quickly routed. Then Panourgias fell back when wounded. With the flanks gone, the Ottomans concentrated everything on the Alamana bridge. Vasilis Bousgos, fighting alongside Diakos, could see what was coming and pleaded with him to retreat. Diakos refused. He remained with 48 men and fought hand-to-hand for hours. When his sword broke and he was wounded, he was taken prisoner. The disproportion — 48 men against the concentrated force of an 8,000-strong army — makes the duration of that stand remarkable.

Brought before Omer Vrioni, Diakos received an offer: convert, enter Ottoman service, and survive. He refused. "I was born a Greek and I will die a Greek," he said. Vrioni ordered his execution by impalement.

The Ottomans commanded Diakos to carry the sharpened pole himself. He threw it down. As he was led away, those present heard him singing — a song about spring, about branches flowering and grass pushing up from the earth, and about the cruelty of dying at such a moment. The song became famous; the image it captured, of a man facing death with bitter irony rather than despair, became central to how Greeks remembered him.

Diakos died from his injuries. One local oral tradition holds that a Greek rebel ended his suffering the following day out of mercy, as he was found near death from the impalement. The exact details of his final hours are not certain; what is documented is that he did not survive and that he did not yield.

Militarily, the Battle of Alamana was a Greek loss. The defensive positions collapsed, the Ottoman advance into Roumeli continued, and Diakos was dead. But his refusal of Vrioni's offer — and his composure in what followed — gave the revolution something that a tactical victory could not have provided. His death circulated through the uprising as a story of what the cause meant, and of what it demanded. He became one of the most recognizable martyrs of the Greek War of Independence.

The Alamana site lies near Lamia in Phthiotis, in the shadow of the same Thermopylae pass where the Spartans had made their own last stand twenty-three centuries before. The parallel was not lost on those who told Diakos's story.