Empires have risen and fallen in their pursuit of precious resources such as oil, gold, tea or spices. But in the first half of the 20th century, an increasingly assertive Imperial Japan relied on a fishier form of wealth to build its military and industrial base: the sardine.

In Japan, sardines are among a group of fish fondly known as “the people’s fish.” Along with Japanese anchovy and round herring, they are collectively known as “iwashi” and have long been a common ingredient in the Japanese diet, whether consumed raw or used in a variety of dishes.

But this small fish, named in records from early 20th century Imperial Japan as “ma-iwashi,” was more than just food. Beginning with the Meiji Restoration in 1868, Japan embarked on its modernization project and aggressive empire-making to become an imperial power. Despite being a latecomer to imperialism, through military annexation and invasion Japan took control of large swaths of Asia.

As a scholar studying the history of the Japanese empire, I have profiled the key role of sardines in the making of Japanese imperialism. With a high fat content, a significant portion of the sardine catch was processed into fish oil, serving as a primary raw material for the empire’s war-oriented chemical industry.

From fish oil to dynamite

Prior to the demand for sardines for chemical manufacturing, sardine oil had long been a byproduct of processing the fish into fertilizer. Through the trading company Suzuki Shoten, the........

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