Nagao Kageharu served as a bushō from the latter part of the Muromachi period to the Sengoku period. He was the fifth head of the Shiroi-Nagao clan.  Along with Hōjō Sōun, Kageharu was a leading figure in the Kantō during a period of turbulent societal change marked by gekokujō, a phenomenon by which those of lower status usurped those of higher status.

In 1443, Kageharu was born as the son of Nagao Kagenobu of the Shiroi-Nagao clan.  The Shiroi-Nagao family became the chief retainer of the Yamauchi-Uesugi family from the time that his grandfather, Nagao Kagenaka, served as the kasai, or head of house affairs, for the Yamanouchi-Uesugi.  After succeeding Kagenaka as the head of house affairs,  Kageharu’s father (Kagenobu) further expanded the power of the Shiroi-Nagao family.  Kageharu also served as a retainer of the Yamanouchi-Uesugi family.  From 1455, he fought against Ashikaga Shigeuji (the Koga kubō) in the Kyōtoku War.  In 1471, Kageharu joined his father in an attack against Shigeuji at Koga Castle.

In 1473, upon the death of Kagenobu, Kageharu inherited the headship of the Shiroi-Nagao family, but the position of head of house affairs to Uesugi Akisada (the head of the Yamanouchi-Uesugi family) was assigned to Kageharu’s uncle, Nagao Tadakage (the head of the Sōja-Nagao clan).  Tadakage was the fifth head of the Sōja-Nagao family.  Although this role was filled by a retainer of a retainer, as an assistant to the deputy shōgun of the Kantō, the role carried significant authority.

The Nagao family was divided between the Shiroi-Nagao, the Sōja-Nagao, the Inugake-Nagao, and the Kamakura-Nagao (later known as the Ashikaga-Nagao family).  The role of kasai, or head of house affairs, was performed on a rotating basis by these families.  Originally, however, these individuals came from the Kamakura-Nagao branch who were the lineal descendants of the Nagao family and, secondly, from the Inugake-Nagao.  If, in the case of these two branches, there were no suitable candidates owing to the absence of a head of the family or a head who was too young, then a candidate would be chosen from among the elders of the Shiroi and Sōja branches.  Nevertheless, upon the murder of Uesugi Noritada, as a consequence of the killing of Nagao Sanekage (the head of the Kamakura branch) and Nagao Norikage (who had become the successor to the Inugake branch), Nagao Kagenaka (Kageharu’s grandfather) followed by Nagao Kagenobu from the Shiroi branch served in the position as head of house affairs for two successive generations.

Based on the above reasoning, the most powerful individual to serve as the next head of house affairs was Nagao Kagehito of the Ashikaga-Nagao branch (the Kamakura-Nagao moved to the Ashikaga manor), but he died early in the year prior to the death of Kagenobu, while his son and heir, Nagao Sadakage, as well as the head of the Inugake-Nagao, Nagao Fusakiyo (the younger brother of Kagehito), were too young to serve as the head of house affairs.  Nagao Tadakage was a veteran who had served in critical roles for the family including as the deputy military governor of Musashi.  Following the demise of his adoptive father (Nagao Tadamasa, who served as the head of house affairs prior to Kagenaka), the selection of Tadakage as the successor to Kagenobu was not unnatural given the prior methodology for filling the position of head of house affairs.  Meanwhile, after having members of the Shiroi-Nagao serve in the role for two successive generations, Uesugi Akisada feared the branch would become too strong, providing another reason to assign the role to Tadakage instead of Kageharu.

Despite the reasons for the decision, Kageharu became deeply resentful toward those involved.  Moreover, during the period that the Shiroi-Nagao held the role of head of house affairs, bushi under the command of the Yamauchi-Uesugi had established relationships with the family by which to receive income and recognition of their rights to their landholdings.  By having the role move from the Shiroi-Nagao to the Sōja-Nagao, these bushi feared the loss of their rights and desired Kageharu to succeed to the position to preserve their security.  In particular, along with transition of the role, issues arose in regard to inherited landholdings leading to clashes between bushi affiliated with one of the families against those affiliated with the other.  In the midst of these uncertainties, Kageharu viewed a series of developments as efforts to suppress the Shiroi-Nagao family, so he decided to fight back in an event known as the Revolt of Nagao Kageharu.

In 1475, Kageharu set about preparing his plans from Hachigata Castle in Musashi Province and, in the sixth month of 1476, launched his rebellion, roundly defeating Akisada’s army in a surprise attack against their base at Ikakko.  In the first month of 1477, he led his forces to another victory over Akisada’s troops, driving them to Kōzuke Province and bringing to an end the Irako War.  Moreover, he allied with opponents of the Uesugi including, among others, Toshima Yasutsune, Toshima Yasuaki, Chiba Noritane, Nasu Akisuke, and Narita Shōtō, expanding the frontline of the battle across the Kantō from Sagami to Shimōsa.

Meanwhile, Ōta Dōkan (the head of house affairs for the Ōgigayatsu-Uesugi family) viewed this as an opportunity to expand his influence in Musashi and attacked.  Kageharu fought valiantly but was stymied across the region by the versatile actions of Dōkan, experiencing a loss of power and authority.  Through the support of Ashikaga Shigeuji (the Koga kubō), Kageharu managed to continue the fight; however, in 1478, Dōkan skillfully arranged a settlement between the Uesugi clan and Shigeuji following many years of conflict, resulting in the loss by Kageharu of the backing of Shigeuji.  As a result, Kageharu was attacked and lost Hachigata Castle to Dōkan.  He fled into a mountainous area of the Chichibu District, but, in the sixth month of 1480, he lost his final base at Hino Castle in a follow-on attack by Dōkan and was ousted from Musashi.

After fleeing for the protection of Shigeuji (the Koga kubō), Kageharu was conferred the title of Lieutenant of the Left Division of Outer Palace Guards, and, while serving as Shigeuji’s messenger, waited for an opportunity to rise again.  In 1486, following the assassination of Dōkan at the Kasuya residence of Uesugi Sadamasa (known as Ōgigayatsu Sadamasa), Kageharu joined Sadamasa who was under attack by Akisada, entered Sagami, and fought against Akisada in the Chōkyō War.  Around this time, he entered the priesthood, but, in 1494, once Shigeuji (who was allied with Sadamasa) settled with Akisada, Kageharu came into conflict with his eldest son, Nagao Kagehide, because Kageharu sought to continue fighting against Akisada while Kagehide, in accordance with the wishes of Shigeuji, sought a settlement with Akisada.  In the end, after abiding by Shigeuji’s wishes, Kagehide was allowed to serve Shigeuji and was recognized by Akisada as the head of the Shiroi-Nagao family.  In addition to losing his position as the head of the family, Kageharu became enemies with his son to the point of potential armed conflict.

In 1505, after the Ōgigayatsu-Uesugi clan surrendered and the Chōkyō War drew to a close, having nowhere else to turn, Kageharu surrendered to Akisada.  After the conflict, Akisada entered the priesthood and adopted the name of Kajun.  Pursuant to a letter, he ordered Nagao Saemon Nyūdō to negotiate with Ise Sōzui (Hōjō Sōun) while, around this period, Kageharu was serving under Akisada.  However, since the Revolt of Nagao Kageharu, Shiroi Castle was occupied by the Echigo-Uesugi family (the original family of Akisada) so Kageharu was not allowed to return.

In 1509, Akisada deployed to Echigo with the aim of subjugating Nagao Tamekage, the deputy military governor of Echigo and a member of Kageharu’s family.  Kageharu viewed this as an opportunity to ally with Tamekage and Ise Sōzui who operated independently in Sagami.  On 6/7 of Eishō 7 (1510), he raised arms from Mount Tsukui in Sagami.  In the seventh month, Kageharu was defeated by the army of the Ōgigayatsu-Uesugi clan (allies of Akisada), retreating from Mount Tsukui.  Soon thereafter, news arrived that Akisada had been killed in action in Echigo.  Then, in a bid to recapture Shiroi Castle, in the eighth month, Kageharu moved his forces to Kōzuke.  Around this time, Akisada’s adopted son, Uesugi Norifusa, was gathering defeated troops at Shiroi Castle, but Kageharu attacked and sought to reclaim the castle.  However, Nagao Kagehide (who had become the head of the Shiroi-Nagao clan), along with local ikki forces and rōnin, or wandering samurai, sided with Norifusa so, ultimately, Kageharu was unable to reclaim the site.  In 1511, Kageharu fled to the Tsuru District in Kai Province.  While there, he relied upon the Uenohara-Katō clan (a provincial landowner in Tsuru) for assistance.  From Tsuru, Kageharu aimed to return again to the Kantō but this plan failed and, in 1512, he lived in exile under the protection of the Imagawa clan in Suruga Province.

On 8/24 of Eishō 11 (1514), Kageharu is regarded to have died in Shiroi Castle at the age of seventy-two.  However, given that Kageharu was in exile in addition to the loyalty of Nagao Kagehide to Akisada and Norifusa as their successor, there is a strong possibility that he was not allowed to return to Shiroi Castle at this time and, in fact, he may have died in exile in Suruga Province.

Beginning in 1476, Kageharu continued his rebellion for several decades, which contributed to a major decline in the power of the Uesugi clan in the Kantō over this period.  Hōjō Sōun praised Kageharu as a superior commander in terms of military tactics and resourcefulness.