Ishikawa Kazumasa (1534–1609) was a prominent Japanese retainer who began serving Tokugawa Ieyasu during his youth. Their relationship began in 1551 when both were hostages under the Imagawa clan. Kazumasa remained a loyal companion to Ieyasu, participating in key events such as the Siege of Terabe in 1558 and the Siege of Marune in 1560. After Ieyasu broke away from the Imagawa following the latter event, Kazumasa became a trusted retainer and administrator in his service.
In 1562, during the Siege of Kaminogo Castle, Kazumasa played a crucial role as Ieyasu successfully negotiated the release of his family from Imagawa Ujizane. Acting as their guardian, Kazumasa undertook this perilous duty with great responsibility. By 1567, Tokugawa forces were divided into two major divisions. Kazumasa was appointed commander of 13 Tokugawa daimyo-vassals, while Sakai Tadatsugu oversaw 18 daimyo-vassals.
Kazumasa fought in several critical battles, including the Battle of Mikatagahara in 1573 and the Battle of Nagashino in 1575. Following Toyotomi Hideyoshi's victory over Shibata Katsuie in 1583, Ieyasu conveyed his congratulations through Kazumasa. However, under Tokugawa orders, Kazumasa and Sakakibara Yasumasa later issued statements denouncing Hideyoshi. Kazumasa served at the Tokugawa headquarters in Komaki during the Komaki-Nagakute Campaign of 1584.
In 1585, Kazumasa became increasingly disillusioned with Ieyasu's defiance of Hideyoshi. Viewing this resistance as reckless, he defected to Hideyoshi’s side. This betrayal forced Ieyasu to overhaul his military organization and defense strategies, as Kazumasa had deep insights into Tokugawa operations.
After Hideyoshi's death and the establishment of the Tokugawa Shogunate, Kazumasa and his family faced punitive measures, losing their fief. Kazumasa eventually retired and spent his remaining years with his son, Ishikawa Yasunaga, until his death in 1609.
See also
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Kyogoku Tadataka
Kyogoku Tadataka (1593–1637) was a Japanese nobleman and the head of the Kyogoku clan during the early 17th century, a pivotal time marked by the Tokugawa consolidation of power. His childhood name was Kumamaro, and he hailed from a lineage claiming descent from Emperor Uda (868–897). Tadataka was the son of Kyogoku Takatsugu and one of his concubines, with his paternal grandfather being Kyogoku Takayoshi.
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Matsudaira Naomasa
The late Muromachi period, also known as the Sengoku period, was an era of continuous conflict and upheaval, often likened to periods of chaos in Chinese history. This turbulent era was brought to an end by Tokugawa Ieyasu, who, with the support of loyal retainers, established the Edo Shogunate and became the ruler of Japan. Among Ieyasu’s descendants, Naomasa Matsudaira, his grandson, played a significant role during the Osaka Siege. He earned praise from his adversary, Nobushige Sanada (Yukimura Sanada), for his valor as a young warrior and maintained strong relations with successive Tokugawa shoguns.
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Shimazu Toyohisa
Shimazu Toyohisa (July 1570 – October 21, 1600), also known as Shimazu Tadatoyo, was a samurai of the Shimazu clan and the son of Shimazu Iehisa. He was the nephew of Shimazu Yoshihiro and held command over Sadowara Castle. Known for his valor, Toyohisa participated in numerous key battles of the late Sengoku period, earning recognition for his bravery and tactical acumen.
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Ikeda Terumasa
Ikeda Terumasa (January 31, 1565 – March 16, 1613) was a Japanese daimyo of the early Edo period, recognized by his court title, "Musashi no Kami," and known as the "Shogun of Western Japan." Terumasa, a distinguished military leader, participated in numerous significant battles during the late Azuchi-Momoyama period. His service at the Battle of Sekigahara earned him control over the Himeji domain. Originally named Araokojimaru, he was the son of Ikeda Tsuneoki and the brother of Ikeda Sen. He later became the heir to Ikeda Nobuteru and held Ikejiri Castle in Mino Province.
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Mori Tadamasa
Mori Tadamasa (1570 - July 31, 1634) was a notable military commander during Japan’s Warring States period and an early Edo-period daimyo. Initially, he governed Kawanakajima Domain in Shinano Province (modern-day Nagano Prefecture) and later became the first lord of Tsuyama Domain in Mimasaka Province (now northern Okayama Prefecture). He founded the Mori family line of the Ako Domain. Tadamasa’s family origins trace back to the Genji (Minamoto) clan, specifically the Kawachi-Genji branch from Kawachi Province (in present-day southeastern Osaka Prefecture), a lineage tied to Emperor Seiwa through his ancestor Yorisada Mori, a great-grandson of the famed Minamoto no Yoshiie.
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Sanada Masayuki
Sanada Masayuki (1547 – July 13, 1611) was a daimyo and prominent lord of Japan's Sengoku period. Head of the Sanada clan from Shinano Province, he served the powerful Takeda clan of Kai Province alongside his father and brothers during Takeda Shingen’s leadership. Following the Takeda clan's decline, Masayuki took charge of the Sanada, and despite limited resources, he established his clan as an independent power under the Toyotomi regime by navigating alliances with dominant clans such as the Tokugawa, Hojo, and Uesugi. Renowned as one of his era's greatest strategists, Masayuki achieved notable victories against the Tokugawa forces in the Battle of Kami River and the Siege of Ueda.
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Sanada Nobuyuki
Sanada Nobuyuki was a renowned samurai of the Sengoku period and the eldest son of daimyō Sanada Masayuki. He was the elder brother of the famous warrior Sanada Yukimura. Nobuyuki’s mother was Kansho-in, Masayuki's wife, and he was married to Komatsuhime (Inahime), the daughter of Honda Tadakatsu and the adopted daughter of Tokugawa Ieyasu. Nobuyuki also had two other wives: Seiin-in, his cousin, and Ukyo, the daughter of Tamagawa Hidemasa.
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Date Hidemune
Date Hidemune was a Japanese daimyō during the early Edo period, born in 1591 as the eldest son of Date Masamune, one of Japan’s most prominent feudal lords. His mother was Shinzo no Kata, a concubine, which affected his future prospects. As a young man, Hidemune lived under the care of Toyotomi Hideyoshi and was given the adult name "Hidemune," adopting one character from Hideyoshi's own name. Hideyoshi granted Hidemune the court rank of junior 5th, lower grade, along with the title of ji-jū, and appointed him as a page to his son, Toyotomi Hideyori.
