Born in Kajiya-chō, in the castle town of Kagoshima in Satsuma, a son of the Satsuma samurai Ōyama Tsunamasa. He was a cousin of the brothers Saigō Takamori and Jūdō and grew up from childhood in the same neighborhood. Kajiya-chō produced many notable figures, such as Ōkubo Toshimichi and Tōgō Heihachirō.
The young Ōyama had joined the radical faction of Satsuma that called for revering the emperor and expelling foreigners, but when the Teradaya Incident occurred, in which comrades gathered at the Teradaya inn in Kyoto were suppressed on the domain's orders, Ōyama too was ordered into confinement at home. This incident, in which comrades of the same domain fought each other, left a deep impression on him.
He fought in the Anglo-Satsuma War, when a British squadron attacked Kagoshima, and saw firsthand the power of Western cannon. Prompted by this, he went to Edo and studied Western gunnery at the school of the Egawa family. This experience became the starting point for his later role in building up the artillery of the Japanese army.
In the Boshin War he led Satsuma's artillery and fought in many places. The cannon he improved are said to have been called "Yasuke guns," after his common name Yasuke. In the attack on Aizu-Wakamatsu Castle he fought on even though he himself was wounded.
On government orders he went to Europe and observed the Franco-Prussian War. He then stayed on in places such as Geneva in Switzerland to study languages and military affairs, mastering the workings of a modern army. He was good at French and became familiar with Western culture.
In the Satsuma Rebellion, when his cousin Saigō Takamori rose in arms with the samurai of Kagoshima, Ōyama had to fight as one of the commanders of the government army. Fighting as an enemy against Saigō, whom he had admired since childhood, was a great anguish, and he is said not to have returned to Kagoshima for a long time afterward.
He married Yamakawa Sutematsu, who had returned home after graduating from an American college. Sutematsu came from Aizu domain and had been inside Aizu-Wakamatsu Castle when Ōyama attacked it. The two became a couple symbolic of the Rokumeikan era, and Sutematsu, while supporting her husband, devoted herself to women's education and nursing.
When the cabinet system was created, he became the first Army Minister in the first Itō Hirobumi cabinet. He long remained at the center of the army, working to build a modern army by adopting Western systems. He was known for a generous character that did not meddle in details.
In the First Sino-Japanese War he landed on the Liaodong Peninsula as commander of the Second Army and captured Lüshun (Port Arthur), a Qing stronghold. After the war he rose to field marshal, one of the army's highest ranks, becoming a leading figure of the Japanese army.
In the Russo-Japanese War he became commander-in-chief of the Manchurian Army, uniting all the army forces fighting in Manchuria, and directed operations with his chief of staff Kodama Gentarō. Ōyama is said to have left detailed planning to Kodama while himself remaining calm and steady, settling the minds of the whole army.
At the Battle of Mukden, the largest land battle of the Russo-Japanese War, he forced the Russian army to retreat and occupied Mukden (now Shenyang). But the Japanese army too had suffered heavy losses and was nearly exhausted, and Ōyama and Kodama told the government that the war needed to be ended soon.
He became Lord Keeper of the Privy Seal, advising the emperor on politics, and supported Emperor Taishō. Though he had great fame as a soldier, he did not become deeply involved in political struggles. In his later years he enjoyed hunting and country life, spending time at his villa in Nasu, Tochigi.
He died of illness while still Lord Keeper of the Privy Seal and was given a state funeral. Born a cousin of Saigō Takamori, he had lived through the great wars of modern Japan, from the Boshin War and the Satsuma Rebellion to the Sino-Japanese and Russo-Japanese Wars. His wife Sutematsu is said to have devoted herself to nursing him.
Saigō TakamoriŌkubo ToshimichiTōgō HeihachirōKodama GentarōŌyama SutematsuYamamoto GonbeeItō Hirobumi
Shibusawa EiichiKuroda KiyotakaItō HirobumiTanaka ShōzōNiijima JōInoue MasaruSaigō TsugumichiMutsu Munemitsu
People of the Meiji period ・ People by period
Based on facts found in textbooks and biographies. Uncertain points are marked as such.