The Revolt of the Iba Clan occurred in the early Sengoku period as an internal conflict between Rokkaku Takayori, the military governor of Ōmi Province and Iba Sadataka, the deputy military governor of Ōmi.

Prelude

In 1460, Takayori inherited the headship of the Rokkaku clan at the age of six.  Upon the outbreak of the Ōnin-Bunmei War, he was eleven.  The decision for the Rokkaku clan to participate with the Western Army is deemed to have been led by Yamauchi Masatsuna (a member of the Rokkaku clan) and Iba Sadataka, the deputy military governor.  Thereafter, with their efforts, the clan got through the Ōnin-Bunmei War but their relationship deteriorated.  In the eighth month of 1479, after an argument erupted between Takayori and Sadataka, Takayori left his residence in Kyōto and fled to the residence of Isshiki Yoshinao.  Thereafter, the Muromachi bakufu made two attempts to subjugate the Rokkaku clan in Ōmi.  This is known as the Chōkyō-Entoku Expedition.  Members of the Rokkaku came together to resist the bakufu army.  In the eleventh month of 1492, Takayori dispatched Masatsuna as a messenger of peace to Ashikaga Yoshiki, the tenth shōgun of the Muromachi bakufu, but he was murdered instead.  In the fourth month of 1493, Yoshiki was deposed in a coup d’ètat orchestrated by Hosokawa Masamoto, the kanrei, or deputy shōgun.  This is known as the Meiō Political Incident.

In the eleventh month of 1494, Masatsuna’s son, Yamauchi Naritsuna was appointed by Ashikaga Yoshizumi, the eleventh shōgun, as the new military governor of Ōmi, causing Takayori to rebel.  The Rokkaku clan remained unstable until a formal peace with the bakufu was reached in the seventh month of 1495.  In 1499, Yoshiki forged an alliance with the Asakura clan of Echizen Province and sought Takayori and Iba Sadataka to betray Yoshizumi in a bid to march upon the capital.  Takayori and Sadataka, however, repelled Yoshiki during his attempt to reclaim his position as the shōgun.

First revolt of the Iba clan

In the tenth month of 1502, after Takayori reproached Sadataka, Sadataka and his family absconded.  In the eleventh month, Sadataka, with the support of Yamauchi Naritsuna, attempted a revival and rebelled.  On 12/26 of Bunki 2 (1502), he attacked and toppled Mabuchi and Nagahara castles.  Takayori departed from Kannonji Castle and, through the assistance of Gamō Sadahide, safely fled to Otowa Castle.

Sadataka proceeded to assault Otowa Castle.  In the third month of 1503, Akazawa Tomotsune, a retainer of Hosokawa Masamoto, rushed forward with reinforcements for the Iba clan.  In the sixth month, Tomotsune returned to Kyōto.  Masamoto then mediated a settlement between Takayori and Sadataka whereupon Sadataka’s son, Iba Rokurō, met with Takayori.  Before long, Rokurō and Yamauchi Naritsuna fled from the capital and sought the support of Masamoto, and in 1540 Sadataka resumed the role of deputy military governor of Ōmi.  In 1511, Ashikaga Yoshitane (formerly known as Ashikaga Yoshiki) was restored as the shōgun.  Yoshitane then ordered Sadataka, in his capacity as the deputy military governor, to collect land taxes for the enthronement ceremony for Emperor Gonara.

Second revolt of the Iba clan

On 2/19 of Eishō 11 (1514), Sadataka and his son, Iba 貞説 (which may have referred to Rokurō) absconded again.  Backed by the Azai and Kyōgoku clans of northern Ōmi who opposed the Rokkaku, Sadataka fought against Takayori in southern Ōmi.

In 1520, the Rokkaku army assaulted Kunori Castle, the base of the Kunori clan who were powerful retainers of the Iba clan.  As a result, the Iba and Kunori clans were expelled from the territory of the Rokkaku.  Owing to the retirement of Takayori, at this time the Rokkaku clan was led by Rokkaku Sadayori who demanded Hosokawa Takakuni to send large vessels from Hyōgo harbor to Lake Biwa.  The vessels could not sail directly there so were pulled via oxcart across a land route from the capital to Ōmi.

Battles between the Rokkaku and the Iba, as well as the Kyōgoku, persisted but, in 1525, the Rokkaku army defeated the Kyōgoku and decimated the Kunori bringing an end to the fighting.  By this time, the territory and positions held by members of the Iba clan had been taken away leaving them with recognition of only their homeland of Iba in the Kanzaki District.  During this period, Takayori and his successor, Rokkaku Ujitsuna, died of illness at the age of nineteen.  Ujitsuna’s younger brother, 承亀, returned to secular life, adopted the name of Rokkaku Sadayori, and endeavored to build a new organization.  Meanwhile, servants of the Iba clan, through the course of the revolt, were folded in as direct retainers of the Rokkaku clan including members of the Ikeda clan.  Upon the death of Ujitsuna, Ikeda Saburōzaemon-no-jō, as a close associate of Ujitsuna, was involved in the succession by Sadayori.

With respect to the relationship between the Rokkaku and the Kyōgoku, during the revolt, in 1523, a succession struggle led to chaos within the Kyōgoku family.  The Kyōguku were subsequently defeated by the Rokkaku and lost their authority as the Azai clan displaced them in northern Ōmi.  Prior to the revolt, the Rokkaku and Kyōgoku both had a degree of influence in the Inukami and Echi districts, but as an outcome of the revolt, the Rokkaku seized power over these districts.  In 1560, after the Azai clan defeated the Rokkaku at the Battle of Norada, the situation changed as the Azai began to move south again.

Theories regarding the factors giving rise to the revolt

Traditionally, the Revolt of the Iba Clan was interpreted as an event leading to the expulsion of the Iba clan owing to the threat posed by the Iba to the Rokkaku.  Specifically, this arose from strengthening their own authority as the deputy military governors of Ōmi vis-à-vis the authority of the Rokkaku in their role as the military governors of Ōmi.  Nevertheless, in the course of further research into the inner workings of the Rokkaku clan, no records have been found indicating a clash of authority between the two clans.  This suggests that other factors played a role in their differences.  One record notes a conflict between the Iba and Mabuchi clans who both served as senior retainers of the Rokkaku.  This is substantiated by the fact that Mabuchi and Nagahara castles which served as the base for the Iba clan and the Nagahara clan (servants of the Iba) were the target of attacks in the first revolt.  Moreover, in the course of the revolt, the Mabuchi clan also fell into ruin while the Nagahara clan became independent of the Mabuchi and, although under the command of the Rokkaku, maintained a direct relationship with the Muromachi bakufu, gaining prominence in the Yasu District.

Another theory points to diplomatic relations in the aftermath of the Meiō Political Incident as causes for the revolt.  As noted, in 1499, when Ashikaga Yoshiki, the tenth shōgun of the Muromachi bakufu, sought the cooperation of the Rokkaku clan in a bid to reclaim his position, Rokkaku Takayori and Iba Sadataka refused him, but others such as the Mabuchi and Gamō clans took steps demonstrating support for his bid.  Having been the target of a subjugation campaign by Yoshiki, Takayori maintained relations with the then-current shōgun, Ashikaga Yoshizumi, and his guardian, Hosokawa Masamoto.  Their relations, however, were not without friction, as demonstrated by the fact that Yoshizumi, immediately after becoming the shōgun, attempted to replace Takayori with Yamauchi Naritsuna as the military governor of Ōmi.  Later, Takayori and Yoshizumi became estranged from one another.  As members of the Rokkaku clan switched their support to the side of Yoshiki, it appears that Iba Sadataka became politically isolated in his support for Yoshizumi and, as a result of incurring the displeasure of Takayori, eventually raised arms.

In fact, it is surmised that Hosokawa Masamoto dispatched the Akazawa clan as reinforcements for the Iba clan and mediated between the two parties with the intention of impeding the spread of the influence of Yoshiki’s faction in Ōmi.  In 1507, Masamoto was assassinated in an event known as the Lord Hosokawa Incident.  This triggered a succession struggle between his adopted sons, Hosokawa Takakuni and Hosokawa Sumimoto known as the Conflict between the Hosokawa.  In a broader context, to the extent this was intertwined with conflict within the ruling Ashikaga family, this is known as the Eishō Disturbance.  In the course of these events, Yoshiki (later known as Ashikaga Yoshitane), with the backing of Ōuchi Yoshioki, reclaimed his position as the shōgun while Takakuni became the head of the Hosokawa-Keichō family (the main branch of the Hosokawa clan).  Meanwhile, Yoshizumi fled the capital and was harbored by the Kunori clan who were servants of the Iba.  In the second month of 1510, Takakuni obtained permission from Yoshiki to subdue the Kunori as well as their lords, the Iba.  The Kunori and the Iba, with the support of Sumimoto, prevailed in battle against Takakuni but the Rokkaku failed to come to their aid.  Consequently, the abyss between the Rokkaku and Iba clans deepened.  Moreover, when the Kunori clan took in Yoshizumi, it is unclear to what extent their lord, Iba Sadataka (who supported Yoshizumi), was involved.  As a result, Sadataka was the subject of the hardline Takakuni to be eliminated and may have been in a position to be abandoned by his lord, Takayori, as well.