Hillel joined the movement in 1936 and in 1942 he moved to Budapest. After the Germans occupied Hungary on 19.3.1944, he and another three comrades were sent to South Transylvania in order to open a new route for the tiyul to Romania in the direction of the city of Brassó (Brašov) beyond the Hungarian border. They were all caught. Hillel was transferred to Debrecen and put into a wagon whose destination was Auschwitz. When the train reached Slovakia, he and some of his friends managed to escape by jumping off the train. Hillel reached the town of Eperjes (Prešov), made contact with comrades from his movement and traveled to Bratislava. Ten of Hillel’s comrades who escaped with him were caught and executed.
In August 1944 the Germans entered Slovakia in order to crush the rebellion that erupted in the Banská Bystrica area. Hillel Hakohen joined the partisans and, with the outbreak of the Slovak uprising, fought with the paratroopers who arrived from Eretz Israel (Palestine) and among them Haviva Reick.
On October 31st his camp was attacked by the Germans. His comrades were killed but Hillel survived by pretending to be dead. He lay wounded for four days until his partisan friends found him and took him to a cabin in the mountains. Ukrainian soldiers who worked for the Germans found him there. Thanks to the forged documents he carried, they did not find out his real identity. Hillel was transferred to the hospital in Banská Bystrica and underwent several operations on his leg. In May 1945 he was liberated by the Red Army.
In 1947, with forged documents, he arrived in Eretz Israel (Palestine) as apilgrim. He moved to Zürich to study medicine. He was a neurosurgeon. Hillel returned to Israel in 1995.