Although Japan had become an industrialized nation in the early 20th century, it remained resource poor. Prior to WWII, limited efforts were made to raise agricultural production, but land reform that would increase tenure for the peasantry was firmly resisted by the right wing government.
Important food imports included salt, sugar, soy beans, and rice. Because Japan was not self sufficient in food production, a substantial number of citizens were always at risk for malnutrition. The need to import rice and other food stuffs was therefore a major stimulus for Japanese incursions into China. With a limited amount of arable land in a heavily-populated island nation, the military-dominated government decided to embark on an aggressive campaign to increase access to natural resources.
In 1943, when the American submarine campaign began to achieve success, the Japanese food situation worsened. Loss of boats and shortage of fuel caused the supply of fish, the principal protein in the Japanese diet, to decline. Toward the end of the war, the return of troops from China to defend the Home Islands further stressed the domestic food supply.
With no way of expanding production by cultivating more land, and the lack of healthy young men to work the existing fields, women and school children became the rural work force. More than a million school children ended their studies and were sent into the countryside to perform agricultural labor.
A poor harvest in 1945, combined with the destruction of the Japanese merchant marine fleet, drastically decreased food supply – rationing reduced rice and other food purchases to 1,500 calorie subsistence levels. Following the American strategic bombing campaign of Japanese cities in mid-1945, the food situation became unsustainable. Japanese civilians would have faced starvation if the country had not surrendered in August.