Lifespan: 14xx to 15xx
Other Names: Rokurō
Title: Governor of Dewa
Lord: Rokkaku Takayori → Ashikaga Yoshizumi
Bakufu: Muromachi – Deputy military governor of Ōmi
Father: Iba Mitsutaka
Children: Sadazumi, 貞説
Iba Sadataka served as a bushō during the late Muromachi and Sengoku periods. He was a landlord in Iba in the Kanzaki District of Ōmi Province.
The Iba were members of the Sasaki clan descended from the Ōmi-Genji. While the Rokkaku were beset by internal discord over issues of succession, Sadataka’s father, Iba Mitsutaka, participated in his capacity as the deputy military governor to manage provincial affairs, strengthening his influence. In 1460, Rokkaku Masataka, the then-current head of the Rokkaku clan, murdered Mitsutaka’s lineal heir as part of an effort to curtail the growing prominence of the Iba clan. In response, the Muromachi bakufu removed Masataka from the line of succession whereupon Rokkaku Yukitaka (later known as Rokkaku Takayori) replaced him as the head of the clan. Mitsutaka’s son, Sadataka, served as the deputy military governor to loyally support Yukitaka.
In 1465, Sadataka went to Kyōto to celebrate the birth of Ashikaga Yoshihisa, the second son of Ashikaga Yoshimasa, the eighth shōgun of the Muromachi bakufu. During the Ōnin-Bunmei War from 1467, Sadataka joined the Rokkaku clan allied with the Western Army led by Yamana Sōzen to fight against the Kyōgoku clan serving on the side of the Eastern Army.
After the Ōnin-Bunmei War, as Yukitaka aimed to strengthen his authority in pursuit of becoming a sengoku daimyō, he sought to control the powers of the noble families along with the temples and shrines. After seizing manors, or shōen, in Ōmi, in addition to the lands of nobles, temples and shrines, and the landholdings of the hōkōshū, or the military organ of the bakufu, he reallocated the territory to kokujin, or provincial landowners, under his command. This was opposed by, among others, Ashikaga Yoshihisa (the ninth shōgun of the Muromachi bakufu), who, in 1487, led a campaign to Ōmi to subdue him, causing Yukitaka to flee to the mountains of Kōka. Sadataka, together with Yamauchi Masatsuna, led kokujin, or provincial landowners, in a guerilla campaign.
Upon the death of Yoshihisa in 1489, the expedition to crush the Rokkaku was suspended. Ashikaga Yoshiki (later known as Ashikaga Yoshitane; the tenth shōgun and successor to Yoshihisa) pardoned Yukitaka, so Yukitaka was restored to his position as the military governor of Ōmi. Together with Sadataka, Yukitaka avoided a calamity. Yukitaka, however, did not return the territory earlier seized and allocated to the kokujin, or provincial landowners, so, in 1491, he was subject to another campaign (this time led by Yoshiki) to eliminate him, known as the first conquest of the Rokkaku in the first phase of the Chōkyō-Entoku Expedition. Yamauchi Masatsuna was summoned by Yoshiki to the Onjō Temple on Otsu and murdered by the army led by Shiba Yoshihiro and Akamatsu Masanori.
Yukitaka fought against Yamauchi Naritsuna (who became the military governor), but with the support of Saitō Myōjun and others, repelled him. Later, once again, he abandoned his base and fled to the mountains of Kōka (or, alternatively, he fled to Ise Province). Yoshiki planned to back as the new military governor the adopted son of Rokkaku Masataka named Torachiyo or Hachirō who originated from the Takashima clan. In 1493, however, Yoshiki was deposed in a coup d’état known as the Meiō Political Incident and replaced by Ashikaga Yoshitaka (the eleventh shōgun, later known as Ashikaga Yoshizumi) who became the eleventh shōgun of the Muromachi bakufu. Yukitaka took advantage of the resulting turmoil to banish Torachiyo. He further prevailed in battle against Naritsuna who had been appointed as the next military governor of Ōmi. In 1495, Yukitaka was pardoned and resumed his position as the military governor. This same year, he changed his name from Yukitaka to Takayori (hereinafter he is referred to as Takayori). As a leader in the Rokkaku army, Sadataka made an expedition to Mino Province which was destabilized by a conflict over succession to Toki Shigeyori, the military governor of the province. This is known as the Battle of Funada.
Yamauchi Masatsuna, who served as the leader of the kokujin and brought them together, was killed during the second conquest of the Rokkaku in the second phase of the Chōkyō-Entoku Expedition. Thereafter, Sadataka consolidated power on a level comparable with Takayori. Fearful of Sadataka’s accumulation of power, Takayori decided to expel Sadataka. In the tenth month of 1502, he invaded the territory of the Iba clan. After losing to the Rokkaku army, Sadataka fled to Kōsai and then joined the Akazawa clan (who supported Hosokawa Masamoto) to mount a counterattack. After Sadataka toppled Aochi, Mabuchi, and Nagahara castles, Takayori abandoned Kannoji Castle and fled for safety to the base of Gamō Sadahide at Otowa Castle. In the sixth month of 1503, through mediation by Hosokawa Masamoto, Takayori and Sadataka settled.
In his later years, Takayori engaged in incessant conflict with his head retainer, Sadataka, known as the Revolt of the Iba Clan. Since his youth, Sadataka served as a deputy military governor to Takayori, helping Takayori to navigate through crises including the Ōnin-Bunmei War and the expeditions by the bakufu to subdue the clan, but eventually he wielded the powers of governance in lieu of his lord, Takayori. Traditionally, it was concluded that Takayori took steps to remove Sadataka out of fear that Sadataka sought to replace him. Based on more recent research, however, the conflict appears to have further nuance. Rather than a power-struggle between Takayori and Sadataka over powers of governance, the authority of the Rokkaku as the military governors as well as the Iba as the deputy military governors of Ōmi was established via events such as the Ōnin-Bunmei War and the expeditions by the bakufu against the Rokkaku, whereas the more fundamental conflict was between the Iba and the Mabuchi clans as senior retainers, exacerbated by a deterioration in the relationship between Takayori and Sadataka owing Takayori’s displeasure at the protection that Sadataka afforded Ashikaga Yoshiki after Yoshiki fled the capital.
In the sixth month of 1507, Hosokawa Masamoto, the kanrei, or deputy shōgun, who earlier orchestrated the coup against Yoshiki, was assassinated in a plot led by Hosokawa Sumiyuki, one of his adopted sons who had earlier been removed from the line of succession. This event is known as the Lord Hosokawa Incident, triggering a protracted succession struggle among his adopted sons backed by their respective factions known as the Conflict between the Hosokawa and, in a broader context, as the Eishō Disturbance. Having lost his patron in Masamoto, Ashikaga Yoshizumi (formerly known Ashikaga Yoshitaka), the eleventh shōgun, turned for support to Takayori in Kutsukidani in Ōmi. Although Takayori initially offered his support as a means to improve relations with the Ashikaga shōgun family, Yoshizumi came into conflict with Takayori (who was in Kyōto at the time) owing to the seizure by the Rokkaku clan of landholdings in Ōmi. Indignant toward Yoshizumi over the situation, and despite efforts by Ise Sadamune to mediate, in the seventh month, Takayori returned to Ōmi.
In the fourth month of 1508, after Ashikaga Yoshiki (the prior shōgun), with the support of Ōuchi Yoshioki (the sengoku daimyō of Suō Province) and Hosokawa Takakuni (one of Masamoto’s adopted sons), ousted Yoshizumi and resumed his former position as the shōgun, Takayori offered refuge after Yoshizumi fled to Ōmi. In 1511, however, following the death of Yoshizumi from illness on 8/14 of Eishō 8 (1511), the next month, Takayori killed Kunori Nobutaka, the lord of Mizuguki-Okayama Castle, who had been sheltering Yoshizumi and then declared his support for Yoshiki. The Iba also had a connection to Mizuguki-Okayama Castle and, under one theory, Sadataka had a role in protecting Yoshizumi which reignited tensions with Takayori.
Sadataka absconded to Kohoku in northeast Ōmi and, with the support of Azai Sukemasa, fought against Takayori from the second month of 1514. Even for those affiliated with the Rokkaku, owing to pressures within the clan, Takayori’s lineal heir, Rokkaku Ujitsuna, rebelled. Despite repeated efforts with the backing of the Azai clan, in the eighth month of 1520, Okayama Castle was felled and Sadataka and his son collapsed. Based on a record from 1525, it is surmised the resistance continued until then. Thereafter, given that the Iba clan appears thereafter as a servant of the Rokkaku, the Iba are deemed to have ultimately obtained recognition of their rights only to their homeland of Iba.
According to one account, Iba 貞説 and his father perished in the second month of 1514.