Hashima Island (Gunkanjima / Battleship Island)

Hashima Island (端島), commonly known as Gunkanjima (軍艦島, "Battleship Island"), is a 6.3-hectare abandoned island lying approximately 15 kilometers southwest of Nagasaki. The island earned its nickname because its silhouette, shaped by successive reclamation and high-rise concrete buildings, resembles a Japanese battleship.

Coal was first discovered on Hashima in 1810. In 1890, Mitsubishi purchased the island and began large-scale development of undersea coal mining operations. Over the following decades, Mitsubishi expanded the island through land reclamation, constructed Japan's first reinforced concrete apartment building (Building No. 30, completed in 1916), and built a self-contained community complete with schools, hospitals, temples, shops, and recreational facilities.

During World War II, the island became a site of forced labor. Beginning in the late 1930s and continuing until Japan's surrender in 1945, mobilized Korean workers and forcibly transported Chinese laborers were brought to Hashima and compelled to work in the undersea coal mines under extraordinarily harsh conditions. Workers labored for 12 or more hours a day in shafts extending up to 600 meters below sea level, enduring extreme heat, inadequate food, and brutal treatment. Escape was extremely difficult — the island is separated from the nearest land (Takashima, about 2.5 kilometers away, and the Nagasaki Peninsula, about 4.5 kilometers away) by open sea, and those caught attempting to flee faced severe punishment.

The exact number of victims remains disputed. Records indicate that approximately 500 to 800 Koreans and around 200 Chinese laborers were brought to the island during the war years. Cremation permit records preserved from the island's village office for 1939–1945 list 122 Korean and 15 Chinese deaths (alongside 1,162 Japanese) from mine accidents, illness, malnutrition and other causes; some accounts place the toll among forced laborers higher.

After the war, coal production continued and the island's population surged, reaching a peak of about 5,260 residents around 1959–1960 (5,259 in 1959 by one count, 5,267 in 1960 by another) — a population density of roughly 83,600 people per square kilometer, often described as the highest in the world at the time. As petroleum replaced coal as Japan's primary energy source, Mitsubishi announced the closure of the mine in January 1974. By April 20, 1974, the last residents had departed, and the island was left to the elements.

For decades, Hashima remained off-limits as its concrete structures deteriorated. In 2009, a small portion of the island was opened to tourists via authorized boat tours from Nagasaki. In July 2015, the island's coal mining facilities were inscribed as a UNESCO World Heritage Site as part of the "Sites of Japan's Meiji Industrial Revolution: Iron and Steel, Shipbuilding and Coal Mining."

The UNESCO inscription proved deeply controversial. South Korea and China protested that the nomination did not adequately address the history of forced labor. The World Heritage Committee required Japan to adopt measures to inform visitors of the full history of each site, including the forced mobilization of workers. However, a 2021 World Heritage Committee decision said the Committee "strongly regrets" that Japan had not yet fully implemented the relevant decisions. As of the early 2020s, on-site information materials at Hashima made little to no mention of Korean or Chinese forced laborers, and Japan's government-run Industrial Heritage Information Centre in Tokyo has been criticized for downplaying or omitting this history.