The majority of the fighting and dying in World War II centered on the Eastern Front and the clash of the Nazi and Soviet armies. The Nazi invasion in June 1941 Operation Barbarossa can be viewed as a series of double envelopments, capturing huge numbers of men and machines. Also called "cauldrons", the great encirclement battles of 1941 cost the Soviet Union dearly. There were approximately 8-11 pockets in 1941, each of which netted more than 100,000 prisoners - most of them would be dead within the next eight months.