Why was Ii Naomasa called the Red Devil?

Ii Naomasa equipped his entire unit — the Ii clan's military force — in distinctive red-lacquered armour. The unit was known as the Ii no Aka Busho or Aka Oni (Red Devils). The uniform red armour made the unit instantly recognisable on the battlefield, intimidated opponents, and gave the Ii clan a powerful visual identity. The tradition continued under his successors and the red-armoured Ii clan remained one of Japan's most recognisable samurai images.

What happened to Ii Naomasa at Sekigahara?

At the Battle of Sekigahara (1600), Ii Naomasa was shot by an arquebus — either during the main battle or in the chaotic pursuit afterward. He was treated but never fully recovered. The wound continued to trouble him, and he died in 1602 — less than two years after the battle — at age 41. His death was attributed to complications from the Sekigahara wound.

Ii Naomasa: The Red Devil of Sekigahara

Ii Naomasa was one of Tokugawa Ieyasu’s most trusted generals — counted among the shitennō (Four Heavenly Kings) alongside Honda Tadakatsu, Sakakibara Yasumasa, and Sakai Tadatsugu. He is best known for the red-armoured unit he commanded, and for a wound taken at Sekigahara that killed him two years after the battle.

Early Life and Tokugawa Service

The Ii clan of Totomi province was nearly destroyed by factional politics within the Imagawa domain during Naomasa’s childhood. He entered Tokugawa service as a young man — tradition places him in Ieyasu’s household from around 1575 — and rose rapidly. [history]

By the 1580s he was commanding the Ii military forces as an independent unit within the Tokugawa army. His abilities as a commander were recognised early; Ieyasu gave him increasing responsibility and, after the Odawara campaign of 1590, a domain assessment of 120,000 koku. [history]

The Red Devils

The Ii clan’s distinctive military identity was their red armour. Naomasa equipped his entire force — from officers to foot soldiers — in matching red-lacquered armour and equipment. The unit became known as the Ii no Aka Busho or simply the Aka Oni (Red Devils). [history]

The uniform appearance served practical and psychological purposes: instant recognition in the chaos of battle, visual demonstration of the lord’s wealth and organisational capacity, and genuine intimidation. A mass of red-armoured warriors approaching was difficult to mistake for anyone else.

Sekigahara

At the Battle of Sekigahara on 21 October 1600, Ii Naomasa fought in the vanguard of Tokugawa’s Eastern Army — one of the first units to engage. His Red Devils struck the Western Army lines early, before the full battle was joined. [history]

During the battle or its aftermath — accounts differ on exactly when — Naomasa was hit by an arquebus shot. He was treated on the field and survived the battle. The wound appeared manageable. [history]

It was not. Naomasa never fully recovered. He died in 1602, less than two years after Sekigahara, aged 41. The wound had continued to deteriorate. The man who fought at Nagashino, Komaki-Nagakute, Odawara, and Sekigahara was killed not by a sword but by a bullet’s slow complications.

Legacy

The Ii clan continued after Naomasa — his son Naotsugu and later successors maintained the red armour tradition and the Hikone domain that became their base. The image of the red-armoured Ii warrior became one of the most recognisable in Japanese samurai culture, and Hikone Castle (which the Ii built) survives as one of Japan’s original castle towers.

Naomasa himself is a figure whose reputation has perhaps suffered from early death: he died before the Tokugawa consolidation was fully complete, and the quieter administrative careers of Honda Tadakatsu’s successors meant the other shitennō were more visible in the Edo period’s peaceful retrospect.