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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Matsudaira Kiyoyasu
Matsudaira Kiyoyasu (September 28, 1511 – November 29, 1535) served as the 7th lord of the Matsudaira clan during Japan's tumultuous Sengoku period. Renowned as the paternal grandfather of Tokugawa Ieyasu, one of Japan's "great unifiers," Kiyoyasu expanded his clan’s influence, bringing all of northern Mikawa Province under his control after subduing the Saigo clan. His power was further symbolized by the construction of Okazaki Castle, a testament to the Matsudaira’s growing dominance.
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Matsudaira Hirotada
Matsudaira Hirotada (June 9, 1526 – April 3, 1549) was a daimyo and lord of Okazaki Castle in Mikawa Province during Japan’s turbulent Sengoku Period. He is best known as the father of Tokugawa Ieyasu, the founder of the Tokugawa shogunate.
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Ikeda Tsuneoki
Ikeda Tsuneoki (1536 – May 18, 1584), also known as Ikeda Nobuteru, was a prominent daimyo of the Ikeda clan and a distinguished military commander during Japan's Sengoku and Azuchi-Momoyama periods. He served under the influential warlords Oda Nobunaga and Toyotomi Hideyoshi. Tsuneoki’s connection to Nobunaga began early, as his mother, Yotokuin, was Nobunaga’s wet nurse and later became a concubine to Oda Nobuhide, Nobunaga's father.
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Oda Nobutaka
Oda Nobutaka (1558–1583) was a samurai of the Oda clan, also known as Kanbe Nobutaka after being adopted as the head of the Kanbe clan, which governed the central region of Ise Province. He was the third son of Oda Nobunaga, born to a concubine named Sakashi. Nobutaka was referred to as "San Shichi," possibly because he was born on the seventh day of the third month in the Japanese lunar calendar. However, there is a theory suggesting he was born twenty days earlier than his elder brother, Oda Nobukatsu, but due to delays in reporting and the low status of his mother’s family, he was acknowledged as Nobunaga’s third son.
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Yamauchi Kazutoyo
Yamauchi Kazutoyo (also spelled Yamanouchi; 1545/1546? – November 1, 1605) was a prominent samurai and retainer who served Oda Nobunaga and later Toyotomi Hideyoshi during Japan's Sengoku and Azuchi-Momoyama periods. His father, Yamauchi Moritoyo, was a descendant of Fujiwara no Hidesato and a senior retainer of the Iwakura Oda clan, which opposed Oda Nobunaga. Moritoyo was also the lord of Kuroda Castle in Owari Province. Kazutoyo is especially renowned for his marriage to Yamauchi Chiyo, whose wisdom and resourcefulness played a key role in his rise to prominence.
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Saito Tatsuoki
Saito Tatsuoki (6 September 1548 - 1573) was a daimyo of Mino Province during Japan's Sengoku period and the third-generation lord of the Saito clan. He was the son of Saito Yoshitatsu and grandson of Saito Dosan. His mother was a daughter of Azai Hisamasa, making him a nephew of Azai Nagamasa and a relative of Oda Nobunaga's first wife, Nohime, who was also a daughter of Saito Dosan.
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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.
