Lifespan: Meiō 2 (1493) (?) to 1/10 of Eiroku 11 (1569)
Other Names: Yasaburō (common)
Title: Secretary for Maintenance
Lord: Nagao Tamekage → Nagao Harukage → Nagao Kagetora (Uesugi Kenshin)
Father: Irobe Norinaga
Siblings: Katsunaga, sister (wife of Kurokawa Kiyozane), Nagatsugu
Children: Akinaga, Nagazane
Irobe Katsunaga served as a bushō during the Sengoku period. He was a retainer of the Uesugi clan and member of the Agakita Group of Echigo Province. Katsunaga served as the lord of Hirabayashi Castle in the village of Hirabayashi in the Koizumi manor in the Iwafune District of Echigo. Katsunaga was born as the son of Irobe Norinaga, a kokujin, or provincial landowner, in Echigo.
A veteran of the clan, Katsunaga served three generations of lords including Nagao Tamekage, Nagao Harukage, and Nagao Kagetora (later Uesugi Kenshin). In 1533, during a revolt by the Jōjō clan, Katsunaga, together with kokujin from the Agakita Group including Honjō Fusanaga, Kurokawa Kiyozane, and Nakajō Fujisuke, abandoned Tamekage and sided with Jōjō Sadanori. Headship of the clan was transferred to Harukage while Tamekage was compelled to retire and live in seclusion. Thereafter, Katsunaga resisted but, in the end, entered into service for Harukage and the revolt gradually receded.
Uesugi Sadazane served as a shugo daimyō during the Sengoku period. Sadazane was a military governor of Echigo Province and the eighth (and final) head of the Echigo-Uesugi family. Around 1538, discussions were raised with Sadazane concerning adoption. Sadazane did not have a son, so plans were made with support of Nakajō Fujisuke (the lord of Tossaka Castle) and others for the adoption by Sadazane of Tokimunemaru (later known as Date Sanemoto) who was the son (Sadazane’s nephew) of a relative – Date Tanemune, a daimyō in Mutsu Province. The Date clan had connections to the Uesugi clan and to Echigo Province. Tokimunemaru’s grandmother on his father’s side hailed from the Uesugi, while his mother was the younger sister of Fujisuke. Tanemune viewed the proposed adoption as an opportunity to further expand his territory.
The Tenbun Conflict was a series of clashes continuing from Tenbun 11 to Tenbun 17 (1542 to 1548) between supporters of Tanemune (the fourteenth head of the Date clan) and those of his eldest son, Date Harumune. Upon the outbreak of this conflict, Katsunaga, along with Honjō Fusanaga and Honjō Kiyozane, sided with Harumune. Subsequently, they attacked Nakajō Fujisuke at Tossaka Castle after he sided with Tanemune. In the midst of the conflict, Ogawa Nagasuke and Ayukawa Kiyonaga instigated a rebellion in the Honjō family and, after the demise of Fusanaga, Katsunaga mediated between the two sides. In 1551, Fusanaga’s son, Honjō Shigenaga forced Nagasuke to take his own life to avenge the killing of his father and, when attempting to kill Kiyonaga, Katsunaga arbitrated between the two parties.
In the era of Kagetora (Uesugi Kenshin), Katsunaga was deeply trusted by Kenshin and participated in battle against Hōjō Ujiyasu in the Kantō. In 1561, at the Fourth Battle of Kawanakajima, he assisted Kakizaki Kageie overcome a crisis and fought as a courageous warrior in the Uesugi army, earning recognition from Kenshin for his contributions. Together with Yasuda Nagahide, he received a certificate of commendation from Kenshin. In 1564, he served valorously during an attack against Sano Castle in Shimotsuke Province and received another letter from Kenshin. Thereafter, Katsunaga served as the commander in charge of Sano Castle for two years. On 1/10 of Eiroku 12 (1569), during the Revolt of Honjō Shigenaga, while laying siege to Shigenaga’s base at Murakami Castle, Katsunaga was killed during a nighttime attack by the defenders. Under another theory, he died of illness. In any event, Katsunaga was succeeded by his son, Irobe Akinaga.
Character and anecdotes
There are many uncertainties regarding Katsunaga’s year of birth. According to one theory, it was 1493, but in a letter co-signed by Honjō Fusanaga and Shibata Tsunasada to Sagoshi Ujifusa, the lord of Sagoshi Castle in the Akumi District of Dewa Province, there is no seal below the name of Katsunaga so, as of 1535, there is a possibility that Katsunaga had not yet attended his coming-of-age ceremony.
In 1557, at the Third Battle of Kawanakajima, he initially refused a demand from Kenshin to deploy, but later complied. In battle formations, Katsunaga used a small war banner with the outline of the sun on a white background. Meanwhile, Hiraga Shigesuke used the exact same banner prompting Katsunaga, in 1563, to protest to a magistrate named Kawada Nagachika on the grounds that he had received this design from Kenshin so it was strange for even Hiraga to be using it. Shigesuke countered by stating that retainers of Saitō Tomonobu used the same design so he did the same. In that case, Nagachika then censured Shigesuke for not refusing to use the banner. After further controversy, Shigesuke was finally prohibited from using the same banner as Katsunaga.
When Kenshin was still named Kagetora, in the Kaetsu region contested among members of the Agakita Group, Kagetora frequently relied upon Katsunaga to arbitrate territorial disputes, internal conflicts, and assorted issues arising among the gōzoku, or wealthy families of the area including the Honjō, the Nakajō, and the Kurokawa.