is the collective name for the conflicts between the Iga ikki and the Oda clan during the Sengoku period. The province was conquered by Oda Nobunaga in 1581 after an unsuccessful attempt in 1579 by his son Oda Nobukatsu. The third insurrection occurred in June 1582, after Oda Nobunaga's deaths during the Honnoji Incident.
The names of the wars are derived from the Tenshà  era name (1573–1592) in which they occurred. Other names for the campaign include or .
Geographically, the Iga region was surrounded by mountains on all sides that could be passed through only via narrow pathways. This, plus the distance of the region from major transportation routes, meant that Iga was easily defendable by a relatively small number of men and was not a priority target for outside forces. The Niki clan had served as shugo of the province for the Ashikaga shogunate, but their control had never been strong and soon weakened further as the shà Âgun's authority diminished. No great warlord rose to take their place, although the Rokkaku to the north and the Kitabatake to the east extended their influence over parts of the province. Instead, as also happened in some neighboring areas, the province came to be controlled by a league (ikki) of the numerous local warrior clans (jizamurai) which had formed to defend the area's independence from outside military forces. The earliest details of the league are unknown, but by the mid-16th century it had been formalized as an organization known as the , or Iga ikki.
Following the Battle of Okehazama in 1560, Oda Nobunaga of Owari province began his rise as a prominent daimyà  of central Japan, rapidly expanding his territory. In 1567 he began his invasion of Ise province, which was then largely under the control of the Kitabatake clan. He slowly caused the Kitabatake vassals to switch to his side, and forced Kitabatake Tomofusa, the head of the clan, to sue for peace following the Battle of Okawachi Castle in 1569. As part of the peace agreement, Tomofusa adopted Nobunaga's son Nobukatsu as his heir, ceding much of his authority to the Oda. In December 1576 Nobunaga and Nobukatsu assassinated most of the remaining Kitabatake leadership (the Mise Incident), cementing their control of Ise.
The young Nobukatsu, who now had control over Ise, decided to expand his domain to include Iga as well. In March 1578, Kai Shimoyama, a former minor Kitabatake vassal from Iga, visited Nobukatsu at his residence in Matsugashima and urged him to invade Iga, listing misdeeds being committed there. These included the expulsion of Niki Yubai, the nominal shugo of Iga, in June of the previous year. Tempted at the possibility of adding Iga to his domain, Nobukatsu dispatched Takigawa Kazumasu to build a castle at Maruyama in Iga to serve as a staging point for the campaign.
Alerted of Nobukatsu's intentions by the construction of the castle, warriors from Iga decided to attack before it had been completed. They attacked Maruyama Castle in broad daylight on November 24, 1578. Taken completely by surprise, Takigawa was forced to withdraw from the castle, which the Iga forces then burned. He reassembled the remnants of his forces at nearby Tsuzumigamine but was again defeated and retreated back to Ise.
Embarrassed and angered by this setback, Nobukatsu wanted to immediately attack Iga but was persuaded to wait by his advisors. Still determined to attack a year later, he formulated a three-pronged invasion the following year and departed Matsugashima on October 6, 1579. The Iga forces soon learned of Nobukatsu's preparations, however, and made plans to meet him. Nobukatsu and his main force of 8,000 men entered Iga through Nagano Pass the following day, but were ambushed as they did so. The waiting Iga troops made heavy use of their knowledge of the terrain and guerrilla tactics to surprise and confuse Nobukatsu's army. He retreated, taking heavy losses as his army became disorganized. The two other, smaller forces (1,500 men led by Tsuge Saburà  through Onikobu Pass and 1,300 men led by Nagano Sakyà Ânosuke through Aoyama Pass) met similar fates, with Tsuge losing his life. According to the Iranki, Nobukatsu's losses numbered in the thousands. Momochi Tanba was among the Iga warriorsàwho ambushed Saburà Â.
The campaign was thus a disaster; not only was Nobukatsu defeated, he had also lost one of his generals. Moreover, Nobukatsu had not consulted with Nobunaga prior to launching his attack. Nobukatsu's attack had been partly motivated by a desire to prove his merit to his father. Instead, Nobunaga was furious when he learned of Nobukatsu actions and threatened to disown him.
On September 30, 1581, Nobunaga launched his own invasion of Iga on a much larger scale. The immediate trigger for this second invasion was a visit by two residents of Iga to Nobunaga's stronghold in Azuchi a month before, during which the men offered to serve as guides for an invasion of the province. Nobunaga agreed and rewarded the men.
By this time Oda Nobunaga was at the height of his power. He controlled most of central Japan, including all of the territories that bordered Iga. He was therefore able to assemble a large army which attacked the province from all directions:
Medieval record has written that Momochi Tanba appeared in this conflict among the Iga warriorsÃÂ who barricaded themselves inÃÂ KashiwaraÃÂ Castle, and there are accounts of him fighting bravely using bow and arrows.
Against this large army of 42,000 men, the Iga defenders only totaled 10,000 at most, and these were spread throughout the province. The Oda forces advanced, torching castles, shrines, and temples, and meeting relatively little resistance. The most significant military actions were the siege of Hijiyama Castle, which had become the rallying point for the northern Iga forces, and the siege of Kashiwara Castle in the south. With the surrender of the forces in Kashiwara Castle on October 8, organized Iga resistance came to an end. During this conflict, a Fortress belonged to Momochi Tanba was burned.
Oda Nobunaga himself toured the conquered province in early November 1581, and then withdrew his troops, placing control in Nobukatsu's hands. After capturing all the castles in Iga on the 11th, Nobukatsu spent time hunting down the remaining Iga forces.
After this conflict, Tanba returned home, changed his name to Shinzaemon, andÃÂ died in 1640 at the age ofÃÂ 85.
InàJune 1582, following the Honnà Â-ji Incident which resulted in Nobunaga beings assassinated, the Iga clans rebelled again. Kitabatake Tomochika, who had been ousted during an uprising in Ise Province fled to Iga. In response to this situation, Oda Nobukatsu ordered his vassal who named Takigawa Katsutoshi to pacify the rebellion. However, the rebellious Iga clan attacked Kashiwara Castle again, the rebellion spread and sparking the Third Tensho Iga Rebellion.
The Iga forcesÃÂ barricaded themselves inÃÂ Kashiwara CastleÃÂ at Nabari District,ÃÂ HijiyamaÃÂ CastleÃÂ atÃÂ Iga District, and also other castles such as the Miyata Castle, Shimabara Castle, andÃÂ Amagoe CastleÃÂ inÃÂ Ahai. Many of Nobuyasu's vassal retreated from Iga exceptÃÂ Ikejiri Heizaemon-no-jo, who stubbornly held down the castle from falling to the hÃÂ n Des of the rebels. In July, Nobuyasu further sent his another's vassals,ÃÂ Takigawa KatsutoshiÃÂ andÃÂ Akiyama Ieyoshi, to subjugate rebellious Iga clans. However, they met stiff resistance, and he requested reinforcements, soÃÂ Ogawa NagayasuÃÂ and others were dispatched. On August 6, the Iga forces launched a night attack, resulting in hand-to-hand combat and the defeat of the Nobuyasu forces.
In September, Nobukatsu's forces decided to attack Miyata Castle. They launched an all-out attack from four directions. Nagayasu, who was in charge of one of the directions, was repelled byàthe Iga forces under Honda RokuemonàandàTaya Jinnojà Â. Meanwhile, the Nagata Castle which was being defended by Nobuyasu's army still struggling against night rains mounted byàthe Iga forces from Hijiyama Castle, so Nagayasu was asked to take over command of the defense. Nagayasu repelled the night attacks from Hijiyama Castle, causing the Iga forces to panic and retreat from the castle. On the other place, Katsutoshi advised Nobuyasu to immediately capture the Shimabara Castle with 1,400 soldiers, including reinforcements fromàTakigawa Kazumasu. However, their attempt to take the castle was repulsed byàthe Iga forced defenders. On September 27, Taira Saemon-no-jo and Ogawa Nagayasu instead received 3,000 reinforcements fromàTsutsui Junkei fromàYamato and captured Shimabara Castle in October. Later in November, Hirazaemon-no-jo suggested that Amagoi Castle would be easy to capture because it was a newly constructed castle, soàTsugawa Yukimitsuàled an army to attack the castlem. However, they failed to subdue the castle. Later,àHijikata Yukihisaàsent an emissary with the order to retreat as Nobukatsu went to Kyoto. Ogawa Nagayasu andàTamaru Naotakeàserved as rear guards and repelled theàpursuingàforce led by Hattori Densuke.
Later in 1583, NobukatsuÃÂ issued a ruling stating that the Ahai District, which was already under Katsutoshi control, that he would defeat the rebel forces once the situation in the Kamigata region had settled. However, whenÃÂ the Battle of ShizugatakeÃÂ broke out that same year betweenÃÂ Hashiba HideyoshiÃÂ andÃÂ Shibata Katsuie, Nobukatsu sided with Hideyoshi. Shibata Katsuie, in a conflicting sense, contactedÃÂ Yamanaka Nagatoshi, a member ofÃÂ the KÃ ÂkaÃÂ clanÃÂ of Iga, to ally with the Iga clan and promote anti-Hideyoshi and Nobukatsu movements in Iga. Furthermore, Kitabatake TomochikaÃÂ , who had rebelled against Nobukatsu in Ise the previous year,ÃÂ fled to Iga and allied with the Iga clan. Furthermore, Nobukatsu's vassals, theÃÂ AkiyamaÃÂ andÃÂ Sawa clansÃÂ of Yamato , joined forces with Tomochika in a rebellion, further contributing to the unstable situation.
Seishà « Gunki,àa military chronicleàandàhistorical bookàofàIse Provinceà(1635-1636), praised Katsutoshi for his fortitude in this third campaign in Iga. After conquering Iga Province, Katsutoshi was given control of Maruyama Castle as a reward.
The espionage and guerrilla tactics developed by the Iga "militias of warrior-peasants" are believed to have formed the basis for the "ninja" tradition of the region. Following their defeat, forces from Iga were hired as auxiliary troops by other military forces.