On 5 April 1944, Bulgarian militiamen as well as German occupation forces of 4th SS Polizei Panzergrenadier Division,[4] the same unit to later that year commit the massacre in Distomo, slaughtered the women and children of Kleisoura in retaliation for the execution of three German soldiers by ELAS close to the village.

The ELAS guerrillas, led by Alexis Rosios from Siatisti ("Captain Ypsilantis"), who were active in the region, had attacked a German military phalanx at Daouli, close to Kleisoura, and had killed a vanguard of three motorcyclists.

After finding the mutilated bodies of the Wehrmacht soldiers close to the local church, the German SS unit went to the homes, broke the doors of the majority of the houses, shot the people within, set fire to the buildings and also killed whom they found in the streets.

[6] Army General Constantine Lianis (Κωνσταντίνος Λιάνης), a war hero, and one of the founders of the Greek secret services (KYP), originated from Kleisoura.

His daughter is Dimitra Liani (Δήμητρα Λιάνη), who became first the lover, and then the third and last wife of Prime Minister Andreas Papandreou.