Nanjung Ilgi: Admiral Yi Sun-sin's War Diary

“I am deeply moved that I have received such an honor, but I am also deeply troubled.” — Admiral Yi Sun-sin, Nanjung Ilgi

Few historical documents from East Asia carry the personal weight and strategic depth of the Nanjung Ilgi (난중일기), the war diary of Korea’s most celebrated naval commander, Admiral Yi Sun-sin. Written in classical Chinese during the devastating Japanese invasions of the 1590s, this extraordinary record stands as one of the most remarkable military memoirs in world history — a window into the mind of a commander who kept writing even as the fate of Joseon Korea hung in the balance.

Recognized today as a National Treasure of South Korea and inscribed on the UNESCO Memory of the World Register, the Nanjung Ilgi is far more than a military log. It is an intimate portrait of a man under extraordinary pressure, a priceless primary source for the Imjin War, and a document that continues to shape Korean national identity centuries after Yi Sun-sin’s death.

Quick Facts: The Nanjung Ilgi at a Glance

Detail	Information
Author	Admiral Yi Sun-sin (이순신)
Period Covered	1592–1598 (the Imjin War)
Language	Classical Chinese
Classification	National Treasure of South Korea
UNESCO Status	Memory of the World Register
Genre	Military diary / Personal memoir
Current Custodian	National Museum of Korea (and related institutions)

1. The Man Behind the Diary: Yi Sun-sin and the Imjin War

To understand the Nanjung Ilgi, one must first understand the catastrophic context in which it was written. In 1592, Japanese forces under the command of Toyotomi Hideyoshi launched a massive invasion of the Korean peninsula, beginning what Koreans call the Imjin War (임진왜란). Within weeks, Japanese armies had swept northward, capturing the capital Hanseong (modern Seoul) and forcing King Seonjo to flee. The Joseon military on land was largely overwhelmed.

At sea, however, the story was dramatically different. Admiral Yi Sun-sin, commanding the Left Jeolla Naval District, mounted a series of devastating counterattacks against Japanese supply lines and naval forces. His victories at Hansando, Busan, and elsewhere denied Japan the naval supremacy it needed to sustain its land campaign. Yi Sun-sin’s innovative use of the geobukseon — the famous “turtle ship” — became legendary, though the diary itself reveals how much of Korea’s naval success rested on meticulous planning, discipline, and sheer determination.

It was during this period of crisis, campaigning, waiting, and worry that Yi Sun-sin kept his diary — writing entries from January 1592 through November 1598, the month of his death in the Battle of Noryang.

2. What the Diary Contains: A Commander’s Daily World

The Nanjung Ilgi — which translates roughly as “War Diary” or “Diary Written in the Midst of War” — is not merely a record of battles and tactics. Its pages reveal the full complexity of life on campaign. Yi Sun-sin wrote about naval engagements and troop movements, but also about illness, grief, dreams, administrative frustrations, and the aching loneliness of a man separated from his family in wartime.

Entries record the admiral receiving reports of Japanese movements, inspecting his fleet, training soldiers, and managing the logistics of supplying thousands of men at sea. He wrote about the weather — particularly important for a naval commander — and about the constant challenges of maintaining morale among exhausted sailors and officers.

Yet the diary also records deeply personal moments. Yi Sun-sin wrote about the death of his mother with raw grief. He recorded dreams in which he encountered the dead. He noted bouts of illness that left him barely able to sit upright, yet from which he still managed to command. These human details transform the Nanjung Ilgi from a military record into something far more moving: the testimony of a man who bore an almost impossibly heavy burden without breaking.

“My heart aches as I think of the soldiers. I cannot sleep.” — Yi Sun-sin, Nanjung Ilgi

Why Is the Nanjung Ilgi Considered a National Treasure?

The question of why this diary merits its extraordinary status — as both a South Korean National Treasure and a UNESCO Memory of the World document — goes beyond simple reverence for a famous admiral. The Nanjung Ilgi satisfies several criteria that historians and heritage institutions use to evaluate documents of exceptional significance.

First, it is a primary source of irreplaceable historical value. The Imjin War was one of the most destructive conflicts in East Asian history, involving Korea, Japan, and Ming China. Official records from the period, while substantial, reflect institutional perspectives and political calculations. Yi Sun-sin’s diary offers something rarer: the direct, day-to-day observations of a key military commander, written in the moment rather than reconstructed afterward. Details about fleet movements, the condition of troops, diplomatic exchanges, and local conditions appear in the diary that are simply absent from official histories.

Second, the diary has extraordinary authenticity. Written in Yi Sun-sin’s own hand, the manuscript is a direct physical link to one of the most consequential figures in Korean history. Scholars can examine not only what he wrote but how he wrote — the character of his brushwork, corrections he made, the density of entries during periods of intense activity versus the sparse entries during illness or despair.

Third, the Nanjung Ilgi has had profound cultural impact. It forms the documentary foundation for Korea’s enduring memory of the Imjin War and of Yi Sun-sin himself. Novels, films, television dramas, and scholarly works across centuries have drawn on the diary as their essential source. The image of Yi Sun-sin that Koreans carry — stoic, selfless, brilliant, deeply human — is built in large part from the pages of the Nanjung Ilgi.

3. The Diary as Literature: Language, Style, and Voice

Written in classical Chinese (漢文, hanmun), the language of scholarship and official life in Joseon Korea, the Nanjung Ilgi nonetheless carries a distinctive personal voice. Yi Sun-sin’s prose is generally terse and unadorned — the writing of a military man rather than a literary stylist. Yet within this economy of language, emotion breaks through with striking force.

Modern Korean readers encounter the diary in translation and adapted editions, since classical Chinese is no longer widely read. Korean-language versions and scholarly commentaries have made the text accessible to general audiences, and it is widely assigned in Korean schools as a foundational text of national history and culture. The diary has also been translated into other languages, bringing Yi Sun-sin’s voice to international readers for the first time.

Scholars of East Asian literature have noted that the Nanjung Ilgi occupies an unusual position: it is not a polished literary work designed for an audience, but an intimate record apparently written for Yi Sun-sin’s own use. This gives it an immediacy and honesty unusual in documents of the period, most of which were composed with an eye toward posterity and political reception.

4. From Manuscript to National Symbol: The Diary’s Later History

After Yi Sun-sin’s death at the Battle of Noryang in November 1598 — reportedly shot by a bullet in the final moments of the final major naval engagement of the war — the diary passed into the custody of his family and descendants. It was not published or widely circulated for some time after his death.

Over the following centuries, as Yi Sun-sin’s reputation grew into something approaching national sainthood in Korea, the Nanjung Ilgi became an object of intense reverence. It was recognized as a National Treasure by the South Korean government, acknowledging both its historical importance and its physical significance as an original manuscript.

The diary’s inscription on the UNESCO Memory of the World Register placed it in distinguished company — alongside documents such as the Magna Carta and the diary of Anne Frank — as a record of exceptional universal significance. This international recognition affirmed what Korean scholars and readers had long maintained: that the Nanjung Ilgi is not merely a Korean artifact but a document of world heritage.

The Nanjung Ilgi Compared: War Diaries in World History

Diary	Author	Period	Significance
Nanjung Ilgi	Admiral Yi Sun-sin	1592–1598	Primary source for the Imjin War; National Treasure and UNESCO Memory of the World
Diary of Samuel Pepys	Samuel Pepys	1660–1669	Intimate record of Restoration England; major literary and historical source
Diary of Anne Frank	Anne Frank	1942–1944	UNESCO Memory of the World; global symbol of Holocaust memory
Duke of Wellington’s Dispatches	Duke of Wellington	Early 19th century	Military correspondence; key source for Napoleonic Wars

5. The Diary’s Legacy in Modern Korea

The Nanjung Ilgi continues to shape Korean culture in the twenty-first century in ways that go well beyond the academic. Yi Sun-sin — as revealed through the diary — has become a cultural archetype in Korea: the selfless public servant who places duty above personal comfort or survival, who endures injustice without abandoning his principles, and who leads by example through suffering rather than from a position of safety.

During periods of national crisis in Korean history — the Japanese colonial period, the Korean War, the difficult years of rapid industrialization — the example of Yi Sun-sin as preserved in the Nanjung Ilgi was repeatedly invoked as a model of Korean resilience and sacrifice. The diary was not simply a historical curiosity; it was an active cultural resource, drawn upon to articulate what it meant to be Korean in the face of overwhelming pressure.

Major Korean films and television productions, including the blockbuster film The Admiral: Roaring Currents (2014), have drawn directly on the diary for dialogue and characterization, bringing Yi Sun-sin’s words to millions of viewers. Scholars continue to publish new critical editions and translations, ensuring that the Nanjung Ilgi remains a living document rather than a museum piece.

Continue Exploring

Deepen your understanding of Yi Sun-sin and the Imjin War with these resources:

Also on Korea Through Time: The Imjin War — Japan’s Invasions of Joseon Korea | The Geobukseon: Inside the Turtle Ship | Joseon’s Military Culture and the Scholar-General Ideal

Nanjung Ilgi: Admiral Yi Sun-sin’s War Diary