Invented by the United States, a large number of troops went to the front line during World War II, and lunch meat was invented because of the low domestic canned food production and high cost. The main materials are pork and potatoes. Although they really don't taste very good, they are relatively comprehensive in nutrition (including protein and starch) because of their low cost (potato and other food doping). It is widely used in the Pacific battlefield. References, the history of World War II, and the history of the Korean War.