Kumamoto Castle: An Indomitable Legacy

While Osaka Castle, Nagoya Castle in Aichi, and many of the most famous Japanese castles were built primarily to project power, Kumamoto Castle was built as an ironclad fortress. Its meticulous construction earned it a formidable reputation in 1607, and this reputation was cemented into a legacy during the Satsuma Rebellion of 1877. Upon his defeat, Saigo Takamori, the legendary “Last Samurai,” admitted that he had been defeated in Kumamoto not by the Meiji conscripts, but by the castle’s architect, Kato Kiyomasa.

Kato Kiyomasa initially felt no need to develop his own castle when he became lord of Higo in 1588, as there were already two castles in the heart of the domain. Apart from the maintenance and expansion of these extant castles, Kato Kiyomasa’s first taste of true castle architecture came when he was selected as one of the many military commanders from around the country to build the first Nagoya Castle in Saga for the regent, Toyotomi Hideyoshi. Castle construction had only taken off in the previous decade, so this gathering of the minds meant exposure to all of the latest and greatest ideas that Kiyomasa would turn into engineering experience. However, his most vital lessons came from the Siege of Ulsan Castle in Korea.

Kato Kiyomasa was selected as a vanguard in the invasion of Joseon (Korea) when the Imjin War began in 1592, and he was placed in charge of fortifying Japanese positions on the peninsula during the 1596 truce. He used this time to hastily construct a castle in the port city of Ulsan that would prove invaluable after the war resumed. At Ulsan, Kiyomasa’s forces were surrounded and besieged twice by the allied forces of Joseon and Ming China. The first siege held for almost a month in 1598, but the Japanese samurai were able to hold off until the allied soldiers retreated. The toll of the battle was heavy, but it was largely the result of starvation and thirst rather than battle. Kiyomasa vowed that no garrison under his command would ever suffer such a fate again. Upon his return to Higo Province, the warlord set out to build an impregnable stronghold that could withstand any onslaught.

Kiyomasa’s plans began with the castle’s geography. The previous Kumamoto Castle was built low into the southwest foot of a hill, which was not ideal for sieges, as enemies could attack from atop the hill behind it. The new fortress was built with the keep on top of the southeast corner of the hill, and walls that went down the sides of the hill to make approaches much slower. Kiyomasa also formed the Tsuboi River as a moat in front of the castle that could be filled using river locks downstream.

Some strategies are more obvious; massive castle walls meant that even cannons at the time would have trouble shooting into the fortress. The “musha-gaeshi” shape was a stroke of genius by Kiyomasa, as it slopes into a sheer drop at the top, meaning it doesn’t provide cover from the guard towers and is impossible to climb. 49 turrets, 18 turret gates, and 29 castle gates atop multiple layers of walls arranged as a labyrinth assured that no enemy could successfully enter without sustaining severe injury.

However, there are even defensive strategies that you might not even think of. For example, Kato Kiyomasa dug over 120 wells inside the castle grounds to ensure troops would never run out of water during a siege (although only about 17 can be found on the castle grounds today). The famous ginkgo tree in front of the castle keep that turns deep gold every fall was originally to ensure soldiers could boil and eat the calorie-dense nuts if they had no other sources of food. In fact, Kato Kiyomasa was so preoccupied preparing for a potential siege that legend says he requested tatami mats woven from dried sweet potato stalks and wall plaster containing taro stalks to create a semi-edible structure.

Since Kumamoto Castle emerged victorious from the 50 day siege against modern artillery in the Satsuma Rebellion, it has inspired generations of Kumamoto residents to persist against all odds. Even as the 400-year-old castle undergoes massive reconstruction following the 2016 earthquake, the Ginkgo Castle continues to take on every challenge and endure as the symbol of our city.