In early March 1944, the occupation forces intensified their operations to "clear" the guerrillas in Western Macedonia. In this context, the operation codenamed "Cuckoo" was organized and started on March 6. The aim of the operation was to eliminate guerrilla activity in Vermio, which the guerrillas used as a base for attacks on the surrounding villages. The operation was carried out by a German battle group under Colonel Augustus Ritter von Eberlein, in cooperation with collaborationist such as the battalion of retired Lieutenant Colonel George Poulos and the battalions of the the Greek National Army (EES).

As part of Operation Cuckoo, Ermakia, a village with a Slavic-speaking population that served as a base for guerrillas of the Greek People's Liberation Army (Ellinikos Laikos Apeleutherotikos Stratos / ELAS), was set as a primary target. From March 6 to 12, the occupying forces launched three attacks on Ermakia. The first attack took place on March 6, when Emberlein's and Poulos' men stormed the village, burning about 10 houses and chasing the guerrillas to the surrounding hills. The second attack took place on March 8. During this attack, Emberlein's group, accompanied by Pullo's group and other EES collaborationists, burned about 50 houses, executed 8 inhabitants, captured about 50 people, and confiscated a significant number of livestock. The prisoners were taken to the village of Amygdala (now Haravgi) and then to a concentration camp in Kozani. The third invasion took place on March 10. During this invasion, the occupying forces came into armed conflict with ELAS men who tried to delay the occupying forces so that the inhabitants could escape safely. During this attack, the guerrilla Evangelos Mantzios was killed.

Despite the end of Operation Cuckoo, the attacks on Hermakia continued. On March 28, the 2nd Battalion of the 7th SS Regiment, in cooperation with the men of the Poulos and the SS, launched a fourth attack against the village and its inhabitants. During this operation, more than 35 civilians were executed, while 10 others were captured. In April 1944, the occupying forces implemented the "Operation May Storm" (Maigenwitter) plan, which aimed to completely control the passes of the Vermio mountain range and encircle the rebel groups. As part of this plan, on April 22, 1944, the SS forces carried out their fifth attack in a row on Ermakia. The village had already been devastated by the previous four raids. However, despite the absence of any inhabitants, the invaders killed two elderly women who had remained in the village.

In total, the Axis occupation forces attacked Ermakia five times between March and April 1944, burning houses, capturing, torturing and executing its inhabitants in cold blood. Although the nature of the research makes it impossible to determine the exact number of victims of the Ermakia massacre, the number of those who were directly executed or who succumbed to wounds caused by the brutality of the occupiers appears to be around 65.

In April 2019, the Greek state, honoring the memory of the victims of the massacre, declared Ermakia a Martyred Village by Presidential Decree No. 29/12.04.2019.