Siege of Odani Castle

What Happened

The Siege of Odani Castle (小谷城の戦い, Odani-jō no Tatakai) was fought between 4 September and 26 September 1573. Oda Nobunaga, the rising warlord of central Japan, attacked the mountain stronghold of Odani Castle in northern Ōmi Province. Its defender was Azai Nagamasa, Nobunaga's former ally and brother-in-law.

The castle fell. The Azai clan was destroyed, and Nagamasa died in the final collapse of the defences. The siege is remembered as the last stand of the Azai and as the first battle of Oda Nobutada, Nobunaga's eldest son and heir.

The site of the fighting lies at coordinates 35.45917 north, 136.27694 east, in what is now Shiga Prefecture. The battle belongs to the Sengoku period, the long age of civil war, and to the opening of the Azuchi–Momoyama period, which began in 1573. It took place in the first year of the Tenshō era (天正, Tenshō), the era name adopted by Nobunaga's patron, Emperor Ōgimachi.

Background

Odani Castle sat on a ridge above the northern shore of Lake Biwa, controlling the roads that linked the capital region with the Japan Sea coast. The Azai had held it since the early sixteenth century. Azai Nagamasa inherited the clan leadership and, in 1564, married Oda Nobunaga's sister, Oichi. The marriage sealed an alliance between two powers whose territories met in Ōmi.

That alliance broke in 1570. Nagamasa joined the Asakura clan of Echizen, the Azai's old overlords, against Nobunaga. The betrayal drew Nobunaga into a punishing war on his northern flank. In June 1570 the two sides met at Anegawa, where Nobunaga and his ally Tokugawa Ieyasu defeated the combined Azai and Asakura forces. The victory did not destroy the Azai. Nagamasa withdrew behind the walls of Odani, and the war dragged on for three more years.

The end came in 1573. Nobunaga drove the shogun Ashikaga Yoshiaki out of Kyoto, ending the Ashikaga shogunate's effective power. Free of that entanglement, he turned north. In August 1573 his army invested Odani Castle, cutting the ridge-line forts that supported it and reducing the outer defences one by one.

Why It Mattered

The fall of Odani removed the Azai clan from the map of Japanese politics. With the Asakura destroyed in the same campaign, Nobunaga's northern border was secure. He could now concentrate on the warlords of western Japan and on the Buddhist armies that still resisted him. The road to national hegemony ran through Ōmi, and after September 1573 that road was open.

The siege also marked the emergence of the next generation. Oda Nobutada, Nobunaga's eldest son, commanded at Odani and is recorded as having fought his first battle there. Nobunaga was training an heir in the same brutal school that had made his own reputation. Nobutada would go on to lead major campaigns before his death in 1582.

The wider consequence was a change of era. Nobunaga's entry into Kyoto and the collapse of Ashikaga authority in 1573 are conventionally treated as the start of the Azuchi–Momoyama period, the three decades of unification that ended the Sengoku age. Odani was one of the battles that made that shift possible.

The Name in Japanese

The Japanese name is 小谷城の戦い, read in kana as おだにじょうのたたかい, and romanised as Odani-jō no Tatakai.

小 — read o here. The character means "small". On its own it is usually read chii-sai or shō, but in this place name it takes the reading o.

谷 — read dani here. The character means "valley". Its common readings are tani and koku. When it follows another element in a compound, the initial consonant often voices, turning tani into dani.

Together, 小谷 (Odani) is the name of the castle's location: "small valley". Place names frequently use readings that differ from a character's everyday pronunciation, and Odani is one of them.

城 — read jō here. The character means "castle". Its native Japanese reading is shiro; the Sino-Japanese reading jō is the one used in formal names and in compounds. The suffix -jō appears in the names of hundreds of Japanese castles.

の — read no. This is a hiragana particle, not a kanji. It links two nouns, marking the first as a modifier of the second. Here it makes "Odani Castle" modify "battle": the battle of Odani Castle.

戦 — read tatakai here. The character means "war" or "battle". Its Sino-Japanese reading is sen, as in 戦国 (Sengoku, "warring states"). The reading tatakai is the native Japanese noun form, and it is the one used in this title.

い — read i. A hiragana character completing the word 戦い. Japanese verbs and many nouns derived from them end in kana that carry no independent meaning; they show how the word is pronounced and inflected.

Read as a whole, the title is a plain descriptive phrase: the battle of Odani Castle. Japanese battle names are usually built this way, with the place name followed by の戦い.

Key Figures

Oda Nobunaga (織田信長) commanded the attacking army. By 1573 he had eliminated the Ashikaga shogunate's power in Kyoto and was the dominant military figure in central Japan. The destruction of the Azai removed one of his most persistent opponents.

Azai Nagamasa (浅井長政) held Odani Castle and led the defence. He had been Nobunaga's ally and brother-in-law before turning against him in 1570. He died when the castle fell in September 1573.

Oda Nobutada (織田信長's eldest son) fought at Odani in what is recorded as his first battle. He was being groomed to succeed his father and would command Oda armies until his death in 1582.

Gamō Ujisato (蒲生氏郷) is associated with the conflict. He was a samurai commander of the Oda sphere whose career was shaped by the campaigns of this period.

Sakai Kyuzo (酒井久蔵) is also associated with the conflict, appearing in records connected to the Odani campaign.