Key Point: A military is only as strong as its soldiers.

In August 1882 in Incheon Bay near Seoul, four Japanese warships were locked in a tense stand-off with two Chinese warships that had brought troops to quell a revolt on the Korean peninsula.

On paper, the Japanese flotilla outnumbered the Chinese, but the hulls of the Japanese ships hid a deadly secret. Less than half of their crews could man their stations.

The Korean peninsula erupted into conflict on July 23. A soldiers’ protest against ill treatment, unpaid wages and poor provisions turned into widespread mutiny. Ousted from power, the former regent of the king set the mutineers upon the government—and against the Japanese advisers working to modernize the Korean army.

Korean soldiers cornered the chief military adviser in his quarters and stabbed him to death. Another 3,000 mutineers attacked the Japanese Legation. The ambassador ordered his men to burn down the compound and then led his staff to a nearby harbor where they caught a ferry to Incheon.

In lashing rain, the rebels chased the Japanese all the way to the port, killing six and wounding five. The roughly two dozen survivors boarded a small boat and cast off. The next morning, the British sloop HMS Flying Fish spotted the row boat and carried the refugees to Nagasaki.

It was a humiliating blow, but the Japanese were not gone for long. The ambassador soon returned to Seoul. This time he had backup.

Four warships sailed alongside to ensure the safe arrival of the ambassador’s government schooner. As ground forces led the ambassador back to Seoul, Kongo, Nisshin, Hiei and Seiki anchored in Incheon Bay. Two Chinese ships also sailed into Incheon at the request of the Korean king.

Tensions between Japan, China and Korea were at an all-time high. Japan was East Asia’s first modern imperialist nation and its neighbors felt threatened by its new ways.

Unknown to the Chinese and Koreans, the Japanese ships were running far below fighting strength. Disease struck down 195 of Kongo’s 330 sailors. Similarly Hiei was down to a third of her regular strength, and Nisshin and Kiyoteru weren’t faring much better. The sailors were lethargic, sluggish and—at worst—paralyzed.

There was no one to relieve them. The warship Fusou—designated to reinforce the mission—was in terrible shape back in Tokyo. The same disease had debilitated 180 of its 309 crew.

Sixteen percent of all disease and injury in the Imperial Japanese Navy in 1882 stemmed from this one sickness. Beriberi. It was a great shame on the nation that one young doctor hoped to cure.

A beriberi big problem

Beriberi—kakke in Japanese—affected all levels of Japanese society, but it became especially prevalent among the urban residents of Edo, the classic name for Tokyo. The disease became known as the “Edo sickness.” Art from the period shows men in wheelchairs afflicted with beriberi.

The malady completely immobilizes its victim, as discussed by English explorer Isabella Bird in her 1880 book Unbeaten Tracks in Japan. “Its first symptoms are a loss of strength in the legs, ‘looseness in the knees,’ cramps in the calves, swelling and numbness.”

“The chronic [form] is a slow, numbing and wasting malady,” Bird continued, “which, if unchecked, results in death from paralysis and exhaustion in from six months to three years.”

At the time, the causes of the disease were unknown. It became the subject of great debate among Western medical personnel in Japan. Basil Hall Chamberlain, a preeminent Japanologist, demonstrated the lack of understanding of the disease’s causes in his 1890 Things Japanese: Being Notes on Various Subjects Connected with Japan.

“The disease springs, in the opinion of some medical authorities, not from actual malaria, as was formerly imagined, but from a climatic influence resembling malaria,” Chamberlain wrote. “Others have sought its origin in the national diet—some in rice, some in fish.”

“In favor of this latter view is to be set the consideration that the peasantry, who often cannot afford either rice or fish, and have to eat barley or millet instead, suffer much less than the townsfolk,” Chamberlain continued.

But the disease wasn’t contagious. We now know that beriberi stems from a lack of vitamin B1, which the body requires for metabolizing carbohydrates and maintaining neurological functions. Without it, a person succumbs to nerve damage and eventually death.

The source of the deficiency was the urban diet. Much of the poor countryside ate a combination of millet and brown rice, which retained their protein-rich husks. However, in the cities, husked and polished white rice had taken over. Easier to store, cook and eat, white rice was a sign of affluence.

Traditional medicine already had remedies for the disease—buckwheat, barley rice, or azuki beans supplied inadvertent boosts of vitamin B1. But “modern” Japan increasingly saw traditional medicine as archaic.

Modern assumptions suggested a bacterial or viral cause. One man found challenging these assumptions an uphill battle.

Beriberi was endemic in the Imperial Japanese Navy. Between 1878 and 1883, the disease incapacitated a third of sailors, on average. Beriberi cases made up almost half of all recorded injuries and disease in the fleet. Yet by 1886, beriberi was gone from the navy.

All thanks to Kanehiro Takaki.

The son of a poor Satsuma samurai family, Takaki was inspired to study medicine by his village Chinese-medicine practitioner. Takaki studied medicine starting in 1866 and, in 1868, answered the call for medical officers to support the Boshin War.

It was a revolutionary period in Japanese history. The West’s opening of Japan’s ports in 1853 spurred Tokyo to modernize. Unhappy with the Shogunate government’s handling of foreign influences, the Satsuma and Choshu domains strove to restore the young Meiji Emperor. This led to a civil war between the allies of the imperial court and those of the Shogunate.

Britain had close ties to the pro-Emperor Satsuma domain. The Imperial forces needed Western medical expertise on the battlefield. William Willis, one of the two physicians at the Legation, found himself running a field hospital at Yogenin Temple in Kyoto.

The efficacy of Western doctors such as William Willis made an impression on the young Takaki. Willis treated hundreds of patients as the fighting spread north—all while revolutionizing wartime medicine. He introduced female nurses and emphasized the need to treat opposition casualties.

Willis’ abilities, knowledge and humanity secured him the post-war presidency of the leading medical institution in Japan, the Tokyo Medical School. But his tenure was short. The Japanese elites decided to follow German medical practices—an authoritative, empirical approach where the patient was more of a test subject than a human being.

Willis lost his job and moved to Satsuma territory in modern-day Kagoshima.

Their close ties with the British and their first-hand experience of Willis’ methods led the Satsuma to create their own school under Willis. Takaki was the school’s first student. He picked up English and acted as teaching assistant and translator during his studies.

Willis pushed Takaki to study abroad. There wasn’t enough money in Satsuma to fund the young doctor’s passage and board. There was just one way Takaki could afford to travel.

He joined the beriberi-riddled navy in April 1872.

Takaki immediately made note of the debilitating effects of beriberi on the fleet. Every few months, around a quarter of its sailors came down with the disease. But why didn’t the British, French and Americans suffer from beriberi?

Naval nutrition

The main reason that the Western navies didn’t have a problem with beriberi was that their sailors ate a balanced diet that included the bran from cereals. This supplied enough vitamin B1 to sustain them. But Western navies had suffered from their own nutritional problems for many years.

Until the 18th century, scurvy was a regular affliction for British crews. The disease causes lethargy and depression, along with seeping sores and partial immobility. Unknown to doctors at the time, scurvy also results from a lack of vitamins—primarily vitamin C, which the body needs to synthesize collagen.

Navies had experimented with the provision of citrus fruits. It was the experience of HMS Suffolk which turned the tide. In 1794, she embarked on a 23-week non-stop voyage to India … and returned with a healthy crew.

Her secret? Daily rations of lemon juice added to the men’s alcoholic grog. The Royal Navy began stockpiling lemons to keep its men healthy. Limes eventually replaced the lemons—the origin of the American slang term for a Brit, “Limey.”

In June 1875, 26-year old Takaki traveled to London to attend St. Thomas’s Hospital Medical School. Over the next five years, he learned medicine on a level that would have been impossible back in Japan. This included exposure to the Royal Navy’s battle with scurvy—a struggle that presaged Takaki’s own campaign against beriberi.

The key to addressing the beriberi problem was a change in thinking. Japan was firmly in the thralls of German laboratory-based empiricism, but Takaki had returned from Britain with a different method: epidemiology.

As a discipline, even as a concept, epidemiology—the medical study of patterns—didn’t yet exist in Japan. But it was the cornerstone of British medicine.