Born to a Ukrainian impoverished family, seven of Berest's fifteen siblings died prematurely. He was orphaned when eleven years old, and raised by his older sisters. From the age of sixteen, he worked as a tractor driver. Berest volunteered into the Red Army in October 1939 and took part in the Soviet-Finnish War as a signaller. When Germany invaded the Soviet Union, he was sent to the front once more. In March 1943, while stationed in the Volkhov Front, Corporal Berest joined the Communist Party. In December, he was sent to the Leningrad Military-Political School (Which at the time was located at Shuya, after being evacuated) and trained as a commissar. After graduation in September 1944, Lieutenant Berest was assigned as Captain Stepan Neustroev's deputy for political affairs ("Zampolit") in the 1st Battalion of the 150th Rifle Division's 756th Regiment.