Ninja

The Iga and Kōga clans have come to describe families living in the province of Iga (modern Mie Prefecture) and the adjacent region of Kōka (later written as Kōga), named after a village in what is now Shiga Prefecture. From these regions, villages devoted to the training of ninjas first appeared.[22] The remoteness and inaccessibility of the surrounding mountains may have had a role in the ninja's secretive development.[21] Historical documents regarding the ninja's origins in these mountainous regions are considered generally correct.[23] The chronicle Go Kagami Furoku writes, of the two clans' origins:

"There was a retainer of the family of Kawai Aki-no-kami of Iga, of pre-eminent skill in shinobi, and consequently for generations the name of people from Iga became established. Another tradition grew in Kōga".[23]
Likewise, a supplement to the Nochi Kagami, a record of the Ashikaga shogunate, confirms the same Iga origin:

"Inside the camp at Magari of the Shogun [Ashikaga] Yoshihisa there were shinobi whose names were famous throughout the land. When Yoshihisa attacked Rokkaku Takayori, the family of Kawai Aki-no-kami of Iga, who served him at Magari, earned considerable merit as shinobi in front of the great army of the Shogun. Since then successive generations of Iga men have been admired. This is the origin of the fame of the men of Iga."[24]
A distinction is to be made between the ninja from these areas, and commoners or samurai hired as spies or mercenaries. Unlike their counterparts, the Iga and Kōga clans produced professional ninja, specifically trained for their roles.[18] These professional ninja were actively hired by daimyos between 1485 and 1581,[18] until Oda Nobunaga invaded Iga province and wiped out the organized clans.[25] Survivors were forced to flee, some to the mountains of Kii, but others arrived before Tokugawa Ieyasu, where they were well treated.[26] Some former Iga clan members, including Hattori Hanzō, would later serve as Tokugawa's bodyguards.[27]

Following the Battle of Okehazama in 1560, Tokugawa employed a group of eighty Kōga ninja, lead by Tomo Sukesada. They were tasked to raid an outpost of the Imagawa clan. The account of this assault is given in the Mikawa Go Fudoki, where it was written that Kōga ninja infiltrated the castle, set fire to its towers, and killed the castellan along with two hundred of the garrison.[28] The Kōga ninjas are said to have played a role in the later Battle of Sekigahara (1600), where several hundred Kōga assisted soldiers under Torii Mototada in the defence of Fushimi Castle.[29] After Tokugawa's victory at Sekigahara, the Iga acted as guards for the inner compounds of Edo Castle, while the Kōga acted as a police force and assisted in guarding the outer gate.[27] In 1614, the initial "winter campaign" at the Siege of Osaka saw the ninja in use once again. Miura Yoemon, a ninja in Tokugawa's service, recruited shinobi from the Iga region, and sent ten ninjas into Osaka Castle in an effort to foster antagonism between enemy commanders.[30] During the later "summer campaign", these hired ninjas fought alongside regular troops at the Battle of Tennōji.[30]

Shimabara rebellion
A final but detailed record of ninjas employed in open warfare occurred during the Shimabara Rebellion (1637–1638).[31] The Kōga ninja were recruited by shogun Tokugawa Iemitsu against Christian rebels led by Amakusa Shirō, who made a final stand at Hara Castle, in Hizen Province. A diary kept by a member of the Matsudaira clan, the Amakusa Gunki, relates: "Men from Kōga in Omi Province who concealed their appearance would steal up to the castle every night and go inside as they pleased."[32]

The Ukai diary, written by a descendant of Ukai Kanemon, has several entries describing the reconnaissance actions taken by the Kōga.

"They [the Kōga] were ordered to reconnoitre the plan of construction of Hara Castle, and surveyed the distance from the defensive moat to the ni-no-maru (second bailey), the depth of the moat, the conditions of roads, the height of the wall, and the shape of the loopholes."[32] — Entry: 6th day of the 1st month

The ruins of Hara castle.Suspecting that the castle's supplies may be running low, the siege commander Matsudaira Nobutsuna ordered a raid on the castle's provisions. Here, the Kōga captured bags of enemy provisions, and infiltrated the castle by night, obtaining secret passwords.[33] Days later, Nobutsuna ordered an intelligence gathering mission to determine the castle's supplies. Several Kōga ninja — some apparently descended from those involved in the 1562 assault on an Imagawa clan castle — volunteered despite being warned that chances of survival were slim.[34] A volley of shots were fired into the sky, causing the defenders to extinguish the castle lights in preparation. Under the cloak of darkness, ninja disguised as defenders infiltrated the castle, capturing a banner of the Christian cross.[34] The Ukai diary writes,

"We dispersed spies who were prepared to die inside Hara castle. ...those who went on the reconnaissance in force captured an enemy flag; both Arakawa Shichirobei and Mochizuki Yo'emon met extreme resistance and suffered from their serious wounds for forty days."[34] — Entry: 27th day of the 1st month
As the siege went on, the extreme shortage of food later reduced the defenders to eating moss and grass.[35] This desperation would mount to futile charges by the rebels, where they were eventually defeated by the shogunate army. The Kōga would later take part in conquering the castle:

"More and more general raids were begun, the Kōga ninja band under the direct control of Matsudaira Nobutsuna captured the ni-no-maru and the san-no-maru (outer bailey)..."[36] — Entry: 24th day of the 2nd month
With the fall of Hara Castle, the Shimbara Rebellion came to an end, and Christianity in Japan was forced underground.[37] These written accounts are the last mention of ninjas in war.[38]

Oniwaban
In the early 18th century, shogun Tokugawa Yoshimune founded the oniwaban, an intelligence agency and secret service. Members of this office, the oniwabanshū ("garden keeper"), were agents involved in collecting information on daimyos and government officials.[39] The secretive nature of the oniwaban — along with the earlier tradition of using Iga and Kōga clan members as palace guards — have lead some sources to define the oniwabanshū as "ninjas".[40] This portrayal is also common in later novels and jidaigeki. However, there is no written link between the earlier shinobi and the later oniwabanshū.

Roles

A page from the Shōninki (1681), detailing a list of possible disguisesThe ninja were stealth soldiers and mercenaries hired mostly by daimyos.[41] Their primary roles were those of espionage and sabotage, although assassinations were also attributed to ninjas. In battle, the ninja could also be used to cause confusion amongst the enemy.[42] A degree of psychological warfare in the capturing of enemy banners can be seen illustrated in the Ōu Eikei Gunki, composed between the 16th and 17th centuries:

"Within Hataya castle there was a glorious shinobi whose skill was renowned, and one night he entered the enemy camp secretly. He took the flag from Naoe Kanetsugu's guard ...and returned and stood it on a high place on the front gate of the castle."[43]
Espionage
Espionage was the chief role of the ninja. With the aid of disguises, the ninja gathered information on enemy terrain, building specifications, as well as obtaining passwords and communiques. The aforementioned supplement to the Nochi Kagami briefly describes the ninja's role in espionage:

"Concerning ninja, they were said to be from Iga and Kōga, and went freely into enemy castles in secret. They observed hidden things, and were taken as being friends"[24]
Later in history, the Kōga ninja would become regarded as agents of the Tokugawa bakufu, at a time when the bakufu used the ninjas in an intelligence network to monitor regional daimyos as well as the Imperial court.[20]

Sabotage
Arson was the primary form of sabotage practiced by the ninja, who targeted castles and camps.

The 16th century diary of abbot Eishun (Tamon-in Nikki) at Tamon-in monastery in Kōfuku-ji describes an arson attack on a castle by men of the Iga clans.

"This morning, the sixth day of the 11th month of Tembun 10, the Iga-shu entered Kasagi castle in secret and set fire to a few of the priests' quarters. They also set fire to outbuildings in various places inside the San-no-maru. They captured the Ichi-no-maru (inner bailey) and the Ni-no-maru."[44]
—Entry: 26th day of the 11th month of the 10th Year of Tenbun(1541)
In 1558, Rokkaku Yoshitaka employed a team of ninja to set fire to Sawayama Castle. A chunin captain led a force of forty-eight ninja into the castle by means of deception. In a technique dubbed bakemono-jutsu ("ghost technique"), his men stole a lantern bearing the enemy's family crest (mon), and proceeded to make replicas with the same mon. By wielding these lanterns, they were allowed to enter the castle without a fight. Once inside, the ninjas set fire to the castle, and Yoshitaka's army would later emerge victorious.[45] The mercenary nature of the shinobi is demonstrated in another arson attack soon after the burning of Sawayama Castle. In 1561, commanders acting under Kizawa Nagamasa hired three Iga ninja of genin rank to assist the conquest of a fortress in Maibara. Rokakku Yoshitaka, the same man who had hired Iga ninja just years earlier, was the fortress holder — and target of attack. The Asai Sandaiki writes of their plans: "We employed shinobi-no-mono of Iga. ...They were contracted to set fire to the castle".[46] However, the mercenary shinobi were unwilling to take commands. When the fire attack did not begin as scheduled, the Iga men told the commanders, who were not from the region, that they could not possibly understand the tactics of the shinobi. They then threatened to abandon the operation if they were not allowed to act on their own strategy. The fire was eventually set, allowing Nagamasa's army to capture the fortress in a chaotic rush.[46]

Assassination
The most well-known cases of assassination attempts involve famous historical figures. Deaths of famous persons have sometimes been attributed to assassination by ninjas, but the secretive nature of these scenarios have been difficult to prove.[12] Assassins were often identified as ninjas later on, but there is no evidence to prove whether some were specially trained for the task or simply a hired mercenary.


Portrait of Oda Nobunaga, by Jesuit painter Giovanni Niccolo, 1583-1590.The warlord Oda Nobunaga's notorious reputation led to several attempts on his life. In 1571, a Kōga ninja and sharpshooter by the name of Sugitani Zenjubō was hired to assassinate Nobunaga. Using two arquebuses, he fired two consecutive shots at Nobunaga, but was unable to inflict mortal injury through Nobunaga's armor.[47] Sugitani managed to escape, but was caught four years later and put to death by torture.[47] In 1573, Manabe Rokurō, a vassal of daimyo Hatano Hideharu, attempted to infiltrate Azuchi Castle and assassinate a sleeping Nobunaga. However, this also ended in failure, and Manabe was forced to commit suicide, after which his body was openly displayed in public.[47] According to a document, the Iranki, when Nobunaga was inspecting Iga province — which his army had devastated — a group of three ninjas shot at him with large-caliber firearms. The shots flew wide of Nobunaga, however, and instead killed seven of his surrounding companions.[48]

The ninja Hachisuka Tenzō was sent by Nobunaga to assassinate the powerful daimyo Takeda Shingen, but ultimately failed in his attempts. Hiding in the shadow of a tree, he avoided being seen under the moonlight, and later concealed himself in a hole he had prepared beforehand, thus escaping capture.[49]

An assassination attempt on Toyotomi Hideyoshi was also thwarted. A ninja named Kirigakure Saizō (possibly Kirigakure Shikaemon) thrust a spear through the floorboards to kill Hideyoshi, but was unsuccessful. He was "smoked out" of his hiding place by another ninja working for Hideyoshi, who apparently used a sort of primitive "flamethrower".[50] Unfortunately, the veracity of this account has been clouded by later fictional publications depicting Saizō as one of the legendary Sanada Ten Braves.

Uesugi Kenshin, the famous daimyo of Echigo province was rumored to have been killed by a ninja. The legend credits his death to an assassin, who is said to have hid in Kenshin's lavatory, and gravely injured Kenshin by thrusting a blade or spear into his anus.[51] While historical records showed that Kenshin suffered abdominal problems, modern historians have usually attributed his death to stomach cancer, esophageal cancer or cerebrovascular disease.[52]

Countermeasures
A variety of countermeasures were taken to prevent the activities of the ninja. Precautions were often taken against assassinations, such as weapons concealed in the lavatory, or under a removable floorboard.[53] Buildings were constructed with traps and trip wires attached to alarm bells.[54]

Japanese castles were designed to be difficult to navigate, with winding routes leading to the inner compound. Blind spots and holes in walls provided constant surveillance of these labyrinthine paths, as exemplified in Himeji Castle. Nijō Castle in Kyoto is constructed with long "nightingale" floors, which rested on metal hinges (uguisu-bari) specifically designed to squeak loudly when walked over.[55] Grounds covered with gravel also provided early notice of unwanted intruders, and segregated buildings allowed fires to be better contained.[56]

Training