Siege of Ōtsu

What Happened

The siege of Ōtsu (大津城の戦い, Ōtsu-jō no tatakai) was fought from 13 October to 21 October 1600, when a coalition army of roughly 15,000 men attacked Ōtsu Castle on the shore of Lake Biwa in central Japan. The castle was held for the Tokugawa cause by Kyōgoku Takatsugu, who commanded the garrison. The attacking force was led by Mōri Terumoto and Tachibana Muneshige, with Suetsugu Motoyasu also among the participants.

The defenders held out for nine days. At the end of that period the two sides negotiated, and Takatsugu surrendered the castle. By then the outcome of the wider war had already been decided elsewhere: Tokugawa Ieyasu had won the battle of Sekigahara, and with it control of Japan. The fall of Ōtsu therefore changed nothing of consequence.

One detail survives from the wider setting of the siege. Contemporary records indicate that local inhabitants brought picnic boxes and gathered at Mii-dera, the temple complex on Mount Hiei, to watch the fighting below.

Background

The siege belongs to the Azuchi–Momoyama period (1573–1603), the decades in which Japan was unified under a succession of military rulers after a century of civil war. It also belongs to the Sengoku period, the long era of "warring states" whose conflicts the Azuchi–Momoyama rulers were bringing to an end. The year 1600 falls in Keichō 慶長, the era name (nengō 年号) then in use, in its fifth year.

Ōtsu Castle stood at a crossing point on Lake Biwa, on the road that connected the capital region with the east. Control of such a castle mattered because armies moving between western and eastern Japan had to pass through this corridor. In 1600 the country was splitting between two great coalitions, and the castles along the routes between them became the objects of the campaign.

Kyōgoku Takatsugu held Ōtsu for the Tokugawa side. The attacking coalition drew on the great western houses: Mōri Terumoto, one of the most powerful lords in Japan, and Tachibana Muneshige, a noted commander from Kyushu. Their roughly 15,000 troops represented a serious investment in taking the castle. Suetsugu Motoyasu also took part in the siege.

The siege ran concurrently with the battle of Sekigahara, the decisive engagement of the campaign. While the western coalition was occupied at Ōtsu, the main armies met in the field, and Ieyasu's victory there settled the war.

Why It Mattered

The siege is remembered less for its result than for its timing. Takatsugu surrendered Ōtsu Castle, which on its own terms was a defeat for the Tokugawa side. But the surrender came after Sekigahara had already been won, so the loss carried no strategic weight. Tokugawa Ieyasu's victory in the field assured his control of all Japan, and a castle changing hands in the days around that victory could not alter the settlement.

The nine-day defence nonetheless had a practical value. By holding the attention of a substantial western force, the garrison kept those troops occupied while the campaign was decided elsewhere. The attackers' numbers — roughly 15,000 — indicate how large a detachment the western coalition was willing to commit to a single castle at the very moment its main army was preparing for a decisive battle.

The siege also illustrates how the war was experienced away from the battlefield. The inhabitants who gathered at Mii-dera on Mount Hiei with picnic boxes to watch the fighting treated the siege as a spectacle visible from a safe distance. That detail, preserved in records of the time, gives a rare glimpse of how ordinary people encountered the conflicts that were deciding the country's future.

The Name in Japanese

The Japanese name is 大津城の戦い, read in kana as おおつじょうのたたかい, and rendered in romaji as Ōtsu-jō no tatakai. It means "the battle of Ōtsu Castle".

Broken down character by character:

• 大 — read ō here. It means "great" or "large". In this name it is the first element of the place name Ōtsu.
• 津 — read tsu here. It means "harbour" or "port", a landing place on a river or lake shore. Together, 大津 (Ōtsu) is "great harbour", the name of the castle town on Lake Biwa.
• 城 — read jō here. It means "castle". When it follows a place name, as in 大津城, it names the castle of that place. The same character can also be read shiro when it stands alone as a word.
• の — read no. This is a possessive particle, written in kana rather than kanji. It links the castle to what follows: "the battle of Ōtsu Castle".
• 戦 — read tatakai here, in its kun reading. It means "war" or "battle". In compound words it appears with the on reading sen, as in 戦国 (Sengoku, "warring states").
• い — read i. This final kana completes the word 戦い (tatakai), the noun form of the verb 戦う (tatakau, "to fight").

A reader meeting the name in a text can therefore parse it as: place name (大津) + castle (城) + possessive particle (の) + battle (戦い). The same pattern — a castle name followed by の戦い — appears in the names of many sieges of the period, which makes the formula worth recognising.

Key Figures

Kyōgoku Takatsugu commanded the garrison of Ōtsu Castle and held it for the Tokugawa side. He defended the castle through nine days of siege before negotiating a surrender on 21 October 1600.

Suetsugu Motoyasu was among the participants in the siege, on the attacking side.

Mōri Terumoto was one of the leaders of the force of roughly 15,000 that laid siege to Ōtsu Castle. He was one of the most powerful lords of western Japan.

Tachibana Muneshige also led the besieging army, alongside Mōri Terumoto. He was a commander from Kyushu.

Tokugawa Ieyasu does not appear among the participants at Ōtsu, but his victory at the battle of Sekigahara, fought concurrently with the siege, decided the campaign. That victory assured his control of all Japan and made the fall of Ōtsu Castle strategically insignificant.