Military confederation of ninja families
The Iga "ikki, full name Iga Sokoku Ikki", also known as the Iga Republic, Iga Confederacy, or Iga Commune, was a republic-style military confederation of ninjas (then known as "shinobi") based in Iga Province during the Sengoku period of Japan. One of the two major schools of ninjutsu, Iga-ryū, is attributed to, and takes its name from, this confederation. During the second half of the 15th century, the ninja families in Iga formed a military confederacy dedicated to the defense of the province. After centuries of rivalry with its northern neighbor, Kōka District in Ōmi Province, eventually Iga worked closely with in alliance with Kōka. In the 16th century, a constitution was drafted based on principles of mutual defense and voluntary association. The confederacy produced legendary figures such as Momochi Sandayu, Fujibayashi Nagato, Hattori Hanzō, Tateoka Doshun, and Shimotsuge no Kizaru. The activities of Iga eventually drew the ire of the Oda clan, who launched invasions in 1579 and 1581. The first invasion was decisively repelled by Iga, but the second overwhelmed the Iga forces and Oda Nobunaga viciously destroyed the confederation. Some ninja were spared and their activities allowed to continue. After Nobunaga's assassination in 1582, Iga and Kōka ninja entered the service of Tokugawa Ieyasu and his descendants into the Tokugawa shogunate.
Primary sources.
Though there are an abundance of primary documents attesting the history of the Iga ninjas, the majority were written decades later during the Tokugawa shogunate and were subject to distortion and exaggeration. "Shinchō Kōki", a chronicle of Oda Nobunaga that was compiled in the early Edo period based on records kept by Ōta Gyūichi, a warrior who followed Nobunaga, is considered by historians to be "mostly factual" and "reliable". It includes mentions of Iga and Kōka soldiers. Most pre-Edo sources are presumed lost in the devastation of Oda Nobunaga's destruction of the Iga "ikki" in 1581.
Five pre-1581 sources detailing military activities by Iga ninja survive. Four of these are diaries or letters from local temples. A December 1541 raid on Kasagi Castle at the request of the Ashikaga shogunate was detailed by Abbot Eishun of Tamon'In, a sub-temple of Kōfuku-ji, in his diary "Tamon'In nikki". "Kyōroku Temmon no Ikki", another diary associated with Kōfuku-ji, describes an attack on Takada Castle in 1556. A letter from Ichiborō a priest of Kongōbu-ji to Futami Mitzuzōin, dated September 12, 1580, describes a counter-attack by the Iga "ikki" against an ally of Oda Nobunaga, Sakaibe Hyōbudaiyū. "Amagoisan rōjō okite kaki" — "Written Regulations for the Siege of Amagoison", a fifth and undated document, describes events from the Tenshō Iga War. While Kawakami Jinichi, a historian at Mie University, dates the document to 1579, because Oda Nobukatsu in that year invaded from Ise Province while the work mentions the invasion of Iga coming from Kōka, historian Stephen Turnbull believes that "Amagoisan" describes the second invasion by Oda Nobunaga in 1581, specifically the force led by Gamō Hidesato along Tamataki route from Kōka.
There also is an extant constitution with an unclear provenance and no specific date or year. It was preserved in Kōka by the Yamanaka family but was attributed to Iga by the historian Ishida Yoshihito because it refers to a "self-governing league" - "sokoku ikki" -, which is what Iga referred to itself as. Based on references within the document, Yoshihito deduced that it was composed between 1552 and 1568.
History.
Formation.
In 15th and 16th century Japan, Iga Province contained some 300-500 small estates and 700 castles and nearby Kōka, in Ōmi Province, had some 53 clans. Both regions were in anarchy, their estates and families constantly engaged in low-level, small-scale feuds and squabbles within and between each region. In Iga, fighting was constant from at least the late 13th century. Bandits also frequently raided the local monasteries. For example, late into the Kamakura period, bandits attacked the Tōdaiji monastery on the Kuroda estate. Incessant warfare broke out in the region 14th century and neighboring "daimyo" posed external threats to Iga. These threats and the banditry necessitated that the local "jizamurai" (high-ranking peasant warriors) form an alliance and develop specialized combat, espionage, and guerilla warfare skills in order to restore peace and order to the province. The remoteness of the hill country in this part of Japan might also have encouraged the development of these skills. Iga was surrounded by mountains and accessible mostly only by narrow paths that permitted only one horse-rider at a time. The militant mountain-monks, "yama-bushi", were also likely an influence as even the bandits in the area wore yellow scarfs that seem to have been copies of those worn by the mountain monks. Reputedly, the units from these two regions often offered their services to nearby provinces as professionally trained, highly trained mercenaries. Specifically, the Iga professionals were sought after for their skill at siege warfare, that is, "shirotori", which included night attacks and ambush. The legendary general Kusunoki Masashige was said to have employed soldiers from Iga to infiltrate and reconnoiter Kyoto in the early 14th century. Turnbull in 2007 argued that this market in mercenary work could have been a motivator for exaggerating the abilities of ninja. However, in 2017, Turnbull questions the existence of such a market at all, contending that, contrary to the mercenary narrative, political self-interest, including continued survival, could also have equally motivated the activities of Iga units in these provinces. The usages of the term "shinobi", specifically "shinobi-mono", later known as ninjas, appearing in the late 1580s and early 1600s, referred to the soldiers from Iga and Kōka. The isolation in these two regions encouraged autonomy, and the communities began organizing into "ikki" - "revolts" or "leagues".
Late 15th century.
By 1477 Iga was known for rejecting the authority of the military governors - "shugo" - appointed by the shogun, and by around 1500 they had formed an "ikki" - a "league". Instead of a local "daimyo" from an aristocratic family replacing the "shugo", leadership remained divided among the "jizamurai" and they formed a league. Records of their military unit, "Iga-shū", appear as early as June 1470, when they assisted the Hatakeyama clan in an attack in the fields outside the Negoro-ji in Wakayama. Another reference to the "Iga-shū" appears in 1482. In October 1485, Iga "kokujin" – another term for "jizamurai" – helped the Hatakeyama defend Mizushi-castle in the neighboring Yamato Province. In 1487, the ninja from Iga and Kōka gained significant fame due to their actions at Magari, which is part of present-day Rittō, Shiga. Shogun Ashikaga Yoshihisa, concerned about the aggressive landgrabs by the Kōka "shugo", Rokkaku Takayori, attacked Takayori. At Magari, Iga and Kōka ninja fought on the side of Takayori in exchange for Takayori recognizing their land ownership. The illness which prematurely killed Yoshihisa may have been at least hastened by, if not caused by wounds suffered during, the guerilla tactics and night attacks by the Iga and Kōka units. Iga troops again were involved with the Rokkaku in 1492.
Mid-16th century.
By the mid-1500s, the services of ninja from Iga and Kōka were in high demand, in use by at least 37 areas. On December 15, 1541, the shogun in Kyoto sent a letter to Iga's governor requesting that the province assist Tsutsui Junshō in his siege of Kasagi Castle. In the morning of December 23, 1541, 70–80 ninja agents from Iga and Kōka infiltrated the castle, set fire to the settlement, and were said to have captured the first and second baileys. Two days later, the armies inside Kasagi sallied out and were defeated, after which the ninjas dispersed. On January 24, 1556, during the Tsutsui siege of Takada Castle in Yamato Province (the site of present-day Takada High School in Yamatotakada, Nara), 11 Iga soldiers attacked the castle and both the castle and the nearby Jōkō-ji were set ablaze.
The "Bansenshūkai", an early Edo period document compiled in 1676 by a member of the Fujibayashi family, alleges an incident from 1558 regarding a ninja commander, Tateoka Doshun, from Iga leading a combined force of Iga and Kōka soldiers against Sawayama Castle. However, according to the historian Stephen Turnbull, this account is full of errors, and accounts not derived from the "Bansenshūkai" do not mention ninja, let alone Tateoka Doshun, at all. Per the account, Rokkaku Yoshikata was campaigning against an alleged rebel retainer, Dodo Oki-no-Kami Kuranosuke, and besieged him. After many days of unsuccessful siege, Yoshikata employed Doshun to aid him. Doshun led a team of 44 Iga ninja and 4 Kōka ninja who carried lanterns Doshun had made with replicas of Dodo's "mon" (family crest). They entered the gates of the castle without opposition and then set fire to the castle. They escaped successfully and in the ensuing panic Yoshikata was able to capture the castle. According to Turnbull, contrary to the account, Dodo in actuality was a retainer of the Rokkaku's enemies, the Azai clan, and when Yoshikata invaded Northern Omi Province in 1559, Dodo was ordered by Azai Nagamasa to hold Sawayama. The historian and travel writer John Man, on the other hand, takes the account at face value and cites this as an example of the fame of the ninjas and of them offering their services for hire.
Around 1560, the confederacy drafted a constitution which included an outline for an alliance with Kōka. Exactly how long the document was extent for, and how widely it applied to the villages of the region, is unknown. In 1560, a highly influential leader within the confederacy, Shimotsuge no Kizaru, attacked Tōichi Castle (present-day Kashihara, Nara), which was commanded by Hashio Shōjirō Tōkatsu. The general's residence was captured, forcing him to flee to Toyoda Castle with his retainer, Dōruku. A man named Ueda and four others were killed.
Conflict with Oda Nobunaga.
The republic soon came in conflict with the rising power of Oda Nobunaga. In 1568, Nobunaga marched to Kyoto to install Ashikaga Yoshiaki as shogun. The Rokkaku clan in southern Ōmi Province allied with the Miyoshi clan and backed Yoshiaki's nephew and rival, Ashikaga Yoshihide, that the Miyoshi had installed in Kyoto. After Rokkaku Jōtei and his sons were defeated during the invasion of Kannonji Castle, they fled first to Kōka and then Mount Kōya. From there they staged a guerrilla war against Nobunaga, assisted by the Iga and Kōka ninja forces. The danger of harassment by this alliance made Nobunaga's control of southern Ōmi insecure, and in 1570 when Nobunaga retreated from the Siege of Kanegasaki back to Kyoto he was forced to go along the north-west shore of Lake Biwa rather than the more direct route through southern Ōmi. "Jizamurai" from Iga and Kōka assisted Jōtei and his sons in raids against Nobunaga, including setting fire to the village of Heso and the southern approaches of Moriyama. On July 6, 1570, these alliance forces were moving down along the Yasugawa river when an army led by Shibata Katsuie and Sakuma Morimasa, generals for Nobunaga, intercepted them at the village of Ochikubo. The alliance was defeated and 780 samurai from the Iga and Kōka "ikki"s were killed, along with the father and son Mikumo Takanose and Mikumo Mizuhara. Stephen Turnbull estimates that 780 casualties must have been enormous for Iga and Kōka, since their armies likely were not very large, and indeed "Shinchō Kōki" makes no reference to that alliance for the next three years.
Around the same time, a monk named Sugitani Zenjūbō and who is presumed to have been a mercenary ninja assassin from either Iga or Kōka, ambushed Nobunaga, fired at him, but failed to successfully assassinate him. Turnbull states that Zenjūbō fired two shots at Nobunaga, both of which were absorbed by Nobunaga's armor. Conversely, John Man cites an interview with a local resident in Kōka City who contends that the monk was from Kōka and attempted only one shot, which missed narrowly missed Nobunaga and passed through his right sleeve. He was executed three years later.
In 1573, the shogun Yoshiaka attempted to thwart the power Nobunaga held over him and allied with the Rokkaku and the Kōka and Iga "ikki"s. Yoshiaki began constructing a castle next to Lake Biwa. The castle was half-finished and the garrison, which included Kōka and Iga troops, was small when Nobunaga attacked. The defenders fled and begged for mercy, and Nobunaga immediately demolished the castle. The same year, archers from Iga