The Greek Civil War grew from the wreckage of the Axis occupation. During the years of occupation, 1941 to 1944, the resistance movement EAM-ELAS — led by the Communist Party of Greece — became the dominant armed force resisting the occupiers across most of the country. When liberation came in October 1944, EAM-ELAS controlled wide areas of rural Greece, while British forces backed the returning Greek government in exile in the cities, especially Athens.

The rivalry broke into open fighting in December 1944 — the Dekemvriana clashes — and EAM-ELAS was ultimately defeated, disarmed under the Treaty of Varkiza in February 1945. What followed was a period of right-wing reprisals against former resistance members and anyone suspected of leftist sympathies. Former partisans formed self-defense units. By the end of 1945, the conflict had escalated into full civil war.

The Hellenic Army's response to the political unreliability it perceived within its own ranks was to isolate suspect personnel. Starting in summer 1946, men who had served with EAM-ELAS or were believed to hold leftist views were transferred into three special units called sapper battalions — Τάγματα Σκαπανέων. By late summer 1947, all three battalions had been dispatched to Makronisos military prison — the Second Battalion arrived first, on 28 May 1947, with the First and Third following within two months — and the total imprisoned population grew to just below 10,000 men.

Makronisos was not, in any conventional sense, a military installation. It was a coercive apparatus. The prison administration combined physical torture, psychological pressure, and hard labor in a systematic campaign aimed at a single goal: forcing prisoners to sign a 'letter of repentance' in which they would renounce their political beliefs, declare their loyalty to Greek nationalism and the monarchy, and join the ranks of prisoner functionaries who would then be used to pressure those who had not yet signed.

The three battalions served different functions in this structure. The Third Sapper Battalion held men who had repented — or who had been coerced into appearing to repent — and who were held up as a model for the others. The Second Battalion held new arrivals and men whose political alignment was uncertain. The First Sapper Battalion was designated the 'Red Battalion' by the prison administration, labeled as containing exclusively 'unpatriotic' elements and committed leftists who resisted conversion. In reality, as historians have established, leftists were distributed across all three battalions; those in the Third acted under the same duress as everyone else, now directed against their fellow prisoners.

On the morning of 29 February 1948, men of the First Sapper Battalion were walking toward the prison camp's auditorium for daily roll call. At the same time, military policemen began detaining prisoners who were sick and others assigned to the prison kitchen — men who had been excused from roll call for those reasons. The policemen beat and insulted those they arrested.

The rest of the battalion could see what was happening. They reacted by shouting 'disgrace' and protesting until an adjutant named Kardaras ordered the policemen to stop. The beating ceased. The crowd quieted. The battalion resumed its march toward the auditorium.

Then the guards opened fire. It was, the evidence indicates, a premeditated provocation. The men dropped to the ground as the military policemen escorting them ran for the barracks. When a major named Karabekios ordered the guards to stop firing and allowed the men to rise, five soldiers were dead and ten more were seriously injured. The battalion's commander, Antonios Vasilopoulos, arrived at the scene and told the survivors he had known nothing of the administration's plans and would investigate and punish those responsible. Whether he believed his own words is not recorded.

The men of the First Sapper Battalion carried their dead to an empty tent. They placed them there with an honor guard. They declared a hunger strike in mourning.

The events of 1 March 1948 — the following day — resulted in further killings. Official reports acknowledged between 11 and 16 additional deaths, while accounts from those who survived and were later interviewed placed the toll considerably higher, at 50 to 60 dead. The discrepancy between official figures and survivor accounts is characteristic of massacres conducted by state institutions; the higher civilian estimates have not been definitively verified, but they have not been refuted either.

For nearly two decades the full story of Makronisos remained largely suppressed. The first detailed public account of the prison's operation appeared in 1966, written by Nikos Margaris, a former detainee who had survived and recorded what he had witnessed. His testimony, and the testimonies of others who came forward over the following years, built the historical record that now exists.

In 1989, the Greek Ministry of Culture declared Makronisos an historical site and placed the military camp's buildings under protection as historical monuments. The island is now accessible to visitors. The barracks and stone structures where the men of the sapper battalions lived under torture and duress still stand on the same ground, visible from the shore of Attica that was never more than a kilometer away during all those years.

The soldiers imprisoned at Makronisos were Greek men who had lived through the German, Italian, and Bulgarian occupation of their country, and who had, in many cases, taken up arms against the occupiers as part of the resistance. After liberation, the political choices they had made — or the political associations they were suspected of holding — marked them as enemies of the state they had fought to free.

They built the prison walls around themselves under forced labor. They signed letters of repentance under torture or refused to sign and endured more. They organized hunger strikes and honor guards for their dead. The first to be killed on 29 February 1948 died walking to morning roll call, shot by guards acting on orders from an administration that had planned the provocation in advance. They were sappers — soldiers trained to build and to clear obstacles — and they were killed, in a pattern that has repeated throughout history, for believing the wrong things in the wrong political moment.

The island of Makronisos is small and barren and very close to the mainland. On a calm day, looking from the shore of Attica across the channel, you could nearly call out to someone standing on it.