Nothing presaged that Kokkalis would one day become a fighter of the Resistance and Minister of Health and Welfare, temporarily also of Education, in the mountain government of the PEEA, and that after the Liberation he would be forced to seek refuge with the partisans and again become Minister of Health, Welfare, and Education in the Provisional Democratic Government formed by the KKE.

But science is part of society. It is a distinct derivative of it, and a person of science who is also Greek cannot (should not) refuse to make their choice. Kokkalis had carried out numerous pioneering interventions in the fields of thoracic surgery, neurosurgery, and cardiac surgery, and his significant involvement in the writing of the two-volume work "Surgery" was an excellent reference for young surgeons.

In 1942, Petros Kokkalis followed his conscience by choosing resistance. He chose to relieve pain and use his organizational talent to set up makeshift hospitals that could care for over 1,000 wounded and sick individuals. And for this choice, he was relieved of his duties and persecuted.

After the end of the civil war, he decided to go to East Germany, where he was able to continue his work until his death.

Professor Petros Kokkalis lived through a difficult period and is one of the few who even today honors Greece, although his homeland did not honor him. He was one of the best surgeons in the world of that time and still a true patriotic Greek, who cared deeply for all the Greek children who found ourselves in Eastern Countries due to the civil war.