Ishikawa Kazumasa

Ishikawa Kazumasa (石川 数正, 1534–1609) was a Japanese notable retainer under Tokugawa Ieyasu, who served him since childhood, when they were both hostages under the Imagawa in 1551.

Ishikawa Kazumasa
石川 数正
Ishikawa Kazumasa in Nagashino.jpg
Ishikawa Kazumasa in Nagashino
Lord of Matsumoto
In office
Personal details
Born1534 (1534)
Mikawa Province
Died1609 (aged 74–75)
Military service
AllegianceTokugawa family crest.svg Matsudaira clan
Japanese crest Imagawa Akadori.svg Imagawa clan
Tokugawa family crest.svg Tokugawa clan
Goshichi no kiri inverted.svg Toyotomi clan
UnitMaru ni Sasa Rindō inverted.png Ishikawa clan
CommandsMatsumoto Castle
Battles/warsSiege of Terabe
Siege of Marune
Siege of Kaminogo Castle
Battle of Mikatagahara
Battle of Nagashino
Battle of Komaki and Nagakute


Kazumasa, also accompanied Ieyasu in the Siege of Terabe 1558, and later at Siege of Marune 1560. After 1560, when Ieyasu abandoned the Imagawa, Kazumasa then became a valued retainer and administrator under him.

In 1562, he took part in the Siege of Kaminogo Castle, when Ieyasu managed to convince Imagawa Ujizane to release his family, Kazumasa acted as guardian of the Imagawa family, which at the time was a very dangerous task.

By 1567, the majority of daimyō forces in the Tokugawa armies were organized in two divisions, each with a separate commander. Kazumasa was placed over the forces of 13 Tokugawa daimyō-vassals and his counterpart, Sakai Tadatsugu, was given command over the forces of 18 daimyō-vassals.

In 1573, He participated in the Battle of Mikatagahara.[1] and 1575 in the Battle of Nagashino.

After Toyotomi Hideyoshi's victory over Shibata Katsuie in 1583, Ieyasu expressed his congratulations to Hideyoshi through Kazumasa. Later, Kazumasa and Sakakibara Yasumasa accordingly issued statements attacking Hideyoshi, due to the Tokugawa's decision. Kazumasa served at the Komaki headquarters during the Komaki-Nagakute Campaign in 1584.

In 1585, Kazumasa, very dismayed by what he saw as Tokugawa's foolhardy path of resistance against Toyotomi Hideyoshi, later he switched sides to Hideyoshi. This inconvenienced Ieyasu, who had to reconstruct his military organization and defensive policies, since Kazumasa had significant knowledge about Tokugawa organization.


After Hideyoshi's death, and the establishment of Tokugawa Shogunate, Kazumasa and his family were punished by being deprived of their fief. Kazumasa then later decided to retire and live with his son Ishikawa Yasunaga, until he died in 1609.


  1. ^ Turnbull, Stephen (2000). The Samurai Sourcebook. London: Cassell & C0. pp. 222–223. ISBN 1854095234.