Who was Motonari?
Mori Motonari (1497–1571) built the largest domain in western Japan out of a small warrior house in Aki Province, near modern Hiroshima. At his death the Mori controlled around ten provinces across the Chugoku region.
He is remembered as the era's most calculating operator: a specialist in dividing his enemies, placing his sons into rival families, and winning through timing and deception rather than mass. His victory at Itsukushima in 1555 against a much larger force is the standard example.
Why is Motonari important?
- He expanded a minor house into the dominant power of western Japan within one lifetime.
- His victory at Itsukushima in 1555 destroyed the Sue and opened the whole Chugoku region to him.
- He placed his second and third sons at the head of the Kikkawa and Kobayakawa houses, converting rivals into branches of his own family.
- The Mori survived Sekigahara reduced but intact, and their descendants in Choshu led the movement that ended the shogunate in 1868.
From a minor house
Motonari inherited very little and spent his early career manoeuvring between the two great powers of the region, the Ouchi and the Amago. He took over the main Mori line in 1523 after the death of his nephew, and by the 1540s had survived a siege of his home castle by an Amago army several times his size.
His method was consistent: keep the appearance of loyalty to the stronger side, absorb neighbours by marriage and adoption, and strike when a rival's internal politics broke down.
Itsukushima, 1555
When Sue Harukata overthrew his own lord Ouchi Yoshitaka, Motonari moved against him. He lured Sue's much larger army onto the narrow island of Miyajima — the site of the famous Itsukushima Shrine with its sea gate — where numbers could not be deployed, then landed at night in a storm and attacked from two directions.
The Sue army was destroyed. Within a few years Motonari had absorbed most of the former Ouchi territories, and by 1566 he had also broken the Amago at the siege of Gassan-Toda Castle.
The three arrows
The best-known story about Motonari is the lesson of the three arrows: he hands each of his three sons a single arrow to snap, then binds three together to show they cannot be broken. It is a good parable and almost certainly a later invention, since the three were not all present at the time it is supposed to have happened.
What is documented is the strategy behind it. Motonari placed his second son at the head of the Kikkawa and his third at the head of the Kobayakawa, so that the two houses that could most easily have opposed the Mori became their support structure instead. This "two rivers" arrangement held for two generations.
Legacy
The Mori under his grandson Terumoto were nominal commanders of the Western Army at Battle of Sekigahara but were kept out of the fighting by a secret arrangement between Kikkawa Hiroie and the Tokugawa side. They lost most of their territory and were reduced to Choshu.
That reduction had a long tail: resentment of the Tokugawa settlement in Choshu is part of the background to the Meiji Restoration of 1868, nearly three centuries later.
