Ninjutsu - Ninjutsu

Japanese: 忍術 - にんじゅつ

One of the Japanese martial arts, it refers to techniques for secretly infiltrating enemy territory or camps for special military or political purposes, and investigating the enemy's movements and secrets. Sometimes, groups of people would take direct action such as assassinations, surprise attacks, and rear-area disruption, dealing a major blow to the enemy's military strength. Compared to general martial arts schools, many of them do not have clear founders or lineages, but they reached a state of near perfection during the Sengoku period. In addition to the three main schools of Iga, Koga, and Kishu (Negoro and Saiga), other well-known schools include the Akutagawa school, Yoshitsune school, Fukushima school, Fuso school, Ninko school, Koyo school, Hakuun school, and Togakushi school. According to the research of Fujita Seiko, who called himself the 14th head of the Koga school, there are 71 ninjutsu schools whose names appear in written records, of which 31 have confirmed documents and records.

[Ichiro Watanabe]

history

The origins of ninjutsu in the broad sense are as old as human life and the history of warfare. Many books, including the ancient Chinese military text "Sun Tzu" ("The Art of War"), teach the use of space and intelligence in the development of a strategy, and depending on the era, they were called saisaku (scouts), yutei (guardians), kansai (spies), yushi (passengers), kōjin (detectives), etc. There is a theory that the origins of our ninjutsu can be traced back to the shinobi used by Prince Shotoku, but in fact it dates back to the end of the Heian period, after the Genpei period, and especially during the turbulent period between the Northern and Southern Courts, when battles became larger in scale and more collective, the use of monomi (scouts) and kanja (detectives) became indispensable. The wise general Kusunoki Masashige hired 48 Iga ninjas to keep an eye on Kyoto's movements, dividing them into three groups with 16 in each group infiltrating the city at any one time. During the Warring States period, which lasted for a century after the Onin War (1467-1477), the offensive and defensive battles between feudal lords intensified, and the activities of ninja and ninjutsu users, who were called by various names such as dakkou (stealing), shinobi (thief), kusa (grass), kamari (bending), rappā (rappā), suha (suiha), and suppa (water wave), became more active and their techniques became more sophisticated.

[Ichiro Watanabe]

ninja

At first, these ninja often served as rangers or bandits familiar with the geography of enemy territories, but gradually their duties diversified beyond simple intelligence gathering (lookouts) to include plundering enemy supplies and weapons (gotou), infiltrating enemy camps at night to disrupt them, and leading night attacks and arson (yochi). This required the ninja's specialized skills and led to unique ideas for the use of gunpowder, etc. They were then employed by daimyo and given special missions.

These include the Fuma clan led by Kazama Kotaro, who was employed by Hojo Ujiyasu of Odawara; the three men (aimi, miwake, metsuke) including Tomita Gozaemon who served Takeda Shingen; Uesugi Kenshin's Nokizaru and Night Thieves, the Sada brothers of the Mori clan, and Aibe Jirozaemon of the Murakami clan. Among these, the existence of organized and collective ninja techniques that were passed down among the local samurai and country samurai of the Iga and Koka regions was becoming increasingly clear. In 1487 (Chokyo 1) during the Chokyo Rebellion, when Shogun Ashikaga Yoshihisa attacked Rokkaku Takayori, the deputy governor of Omi, he performed a miraculous feat at the camp in Kamari (Ritto, Shiga Prefecture) and became famous overnight. From the Muromachi to the Sengoku period, he became famous as a leader of the Iga ninja (jonin), Fujibayashi Nagato no Kami in the north, Momochi Sandayu in the south, and Starting with Hattori Hanzo of Yono, the area produced many masters of the hidden ninja art, including Igazaki Dojun of Tateoka, Kido Yazaemon of Otowa, Kizaru and Kozaru of Shimotsuge, Hidari of Ueno, Yaemon of Yamada, Konan of Kobe, Taroshirou and Tarozaemon of Kamiyama, Ooi Magodayu of Nomura, and Kotaro of Shindo.

Later, in 1581 (Tensho 9), when Oda Nobunaga invaded Iga, these local samurai tried to unite to oppose him, but were defeated by Nobunaga's overwhelming military forces. Many of the local samurai fled from his strict pursuit and fled to Yamato, Yamashiro, Tamba, Kishu, Kawachi, Ise and other places. However, their skills were eventually recognized and they served daimyo such as Maeda Toshiie and Fukushima Masanori, spreading the orthodox Iga ninjutsu to the provinces.

Prior to this, the Hattori clan of Yono had left their homeland to serve the Matsudaira clan of Mikawa (later the Tokugawa clan), but when Ieyasu, who was then in Sakai, Senshu, fell into a difficult situation during the Honnoji Incident in 1582, Hanzo's son, Hanzo Masanari, succeeded in mobilizing 200 Iga and 100 Koga ninjas, and safely passed Ieyasu and his party over the Kabuto Pass and delivered them to Okazaki. As a result of this feat, 200 Iga ninjas were employed under Hanzo's control. Meanwhile, Koga ninjas performed remarkably well, with over 100 from Koga rushing to the rescue of the siege of Fushimi, which was a prelude to the Battle of Sekigahara in 1600 (Keicho 5), and over 70 of them were killed in battle. To reward them for their achievements, Ieyasu organized the Koga Hyakunin-gumi and gave them the rank of Yoriki.

At this stage in the early modern period, ninjutsu had not yet formed into the modern schools of archery, horseback riding, swords, and spears. Ninjutsu techniques did exist, and their tactical necessity was widely recognized, but they were closed, secret arts that were only passed down by word of mouth and by physical training, and were rarely written down. In addition, they had little ethical character, and there was a strong perception that their practical use was something that only low-ranking people (genin) should be involved in, and that only those in special groups should practice them. In the Shimabara Rebellion in 1637 (Kan'ei 14), 100 people, including Mochizuki Hyodaifu, a local Koga samurai, bravely participated in the siege of Hara Castle, but did not achieve any military success. This was the last deployment, and medieval ninja activities came to an end, and they were destined to be forgotten in the future.

[Ichiro Watanabe]

The Creation of Ninja Scrolls

During the reign of the fourth shogun, Tokugawa Ietsuna, the shogunate-han system entered a period of stability and a trend towards civil rule grew stronger. There was almost no need to send spies around the country to monitor the movements of the outside domains, as had been the case at the beginning of the shogunate. The medieval art of stealth gradually lost its raison d'être, and the glory and pride of the ninja groups faded over the years, making it difficult to pass on the techniques.

For this reason, within the ninja groups, who faced the threat of extinction, there was a growing movement to collect secret ninja techniques and weapons used by skilled ninjas of the past, and to systematize and theorize them in the same way as the preceding martial arts, and to clarify the status of ninjutsu as a modern martial art. Representative ninja books created during this period include the four volumes of "Ninpiden" (Ninja Secret Teachings) compiled in 1655 (Shoo 4) by Hattori Minokami Kiyonobu, which focuses on the various traditions and ninja tools handed down in the Hattori Hanzo family, the leader of the Iga ninja, and the four volumes of "Ninja Secret Teachings" (Ninja Secret Teachings) compiled in 1676 (Enpo 4) by Fujibayashi Samuji Yasutake of Yufune near the Koga border, who is said to be a descendant of Iga jounin Fujibayashi Nagatonokami. There are three examples: "Mansenshukai" (Mansenshukai) in 6 volumes and 22 volumes; and "Shoninki" (Shonin Record) in 3 volumes, written five years later in 1881 (Enpo 9) by Toiichi Mizuko Masatake, who was in fact a military scholar of the Shinkusunoki school of the Kishu domain called Natori Sanjuro Masatake, in which he discusses the correct way of ninjutsu, focusing on techniques and mental methods.

Among them, "Bansenshukai" compares and examines the ninjutsu and ninki devised by 11 representative ninjas from Iga and Koga, as well as the various schools of the time, and divides it into six chapters: Shoshin, Shochi, Yonin, Innin, Tenji, and Ninki. It systematically and specifically describes ninjutsu in general based on Confucian ethics, while also using the Chinese Ming Dynasty military book "Bubishi", and can be said to be a great work worthy of being considered the canon of both the Iga and Koga schools. The emphasis on the seishin is that it is the basis of all actions, and if a skilled ninja harbors evil intentions, ninjutsu will quickly turn into the art of a thief, and it strongly emphasizes the mental and legal aspects. "Shoninki" takes exactly the same position, and describes it with an emphasis on the mental rather than the technical aspects.

[Ichiro Watanabe]

Ninja Techniques

It has been pointed out that the techniques of the ninja that emerged mainly in Iga, Koga and Kishu have their roots in the techniques of the Kujigoshinho (Nine Character Self-Defense Technique) and Sankaku (Mountaineering) used by Shugenja (mountaineering monks) in the Middle Ages. However, the aforementioned "Shoninki" states that there are four types of ninjutsu: (1) sound ninja, (2) order ninja, (3) lifeless law ninja, (4) like an illusion ninja, (5) like a shadow ninja, (6) like a flame ninja, (7) like a dream ninja, (8) like a sound ninja, (9) like a There are ten types of ninja: (10) Ka-nin, (11) Ninja like a sky ninja, and (12) Ninja like a sky ninja. In the "Bansenshukai," there are two types of ninja: Yang ninja and Yin ninja. Yang ninja is the art of entering the enemy's territory while revealing one's appearance by using cunning and scheming (subterfuge), while Yin ninja is the art of hiding one's appearance from the public eye, waiting for the enemy's openings, and using special tools and devices (ninja weapons and tools) to sneak in. This hiding is, so to speak, a technique of switching between reality and fiction, changing the position of reality and fiction according to the enemy's actions, skillfully blinding the enemy's eyes, hiding one's appearance to escape from difficult situations, and freely appearing and disappearing in enemy territory.

In addition to the five techniques of Mokuton, Katon, Doton, Kinton, and Suiton, they also applied all manner of phenomena in the world, from humans, birds and animals, fish, and insects to the sun, moon, stars, clouds and fog, thunder and lightning, wind and rain, etc. However, to execute these techniques, agile and strong physical strength and strong mental strength were required, and daily training of both the body and mind was required, that is, the acquisition of physical strength such as brisk walking, stealth walking, jumping, climbing, diving, breathing control, and willpower, as well as the cultivation of mental concentration and endurance. Furthermore, training in low-light vision, far-sightedness, and far-sightedness, which are essential for nighttime undercover activities, was also emphasized. Although ninjas are always at risk to their lives, they state that "fame and glory are useless. The main goal should be to survive with one's life intact (report back), and to do whatever it takes to escape."

[Ichiro Watanabe]

Clothing and disguises

Their clothing was light and airy, based on mountain wear, and included not only black masks and black clothing, which were convenient for nighttime activities, but also dark brown or persimmon-colored clothing on the outside and grayish brown on the inside for camouflage. They often infiltrated enemy territory under cover of night, sometimes taking advantage of heavy rain or fires, or blending in with the crowds at festivals, fights, and other disturbances. They sometimes disguised themselves, but the seven types they disguised were komuso, monks, mountain ascetics, merchants, hokashi, sarugaku, and tsunenari, which are called the art of going out from all directions. The six portable items - a straw hat, a grappling rope, a slate pencil, medicine, a three-foot hand towel, and a bamboo pole (a fire-starting device) - were called the "Six Tools of the Ninja". Food such as dried abalone, dried squid, and pickled plums, as well as rolled diamonds, shuriken, needles, and explosives were also hidden in their pockets.

[Ichiro Watanabe]

Ninja tools and weapons

Various methods and weapons were developed for sneaking into enemy territory and conducting reconnaissance, with each school inventing special tools and unique devices, and the use of gunpowder advanced to the point that the number of types numbered in the hundreds. The "Bansenshukai" classifies these into the following four categories.

(1) Climbing tools (ladders and ropes): knotted ladders, flying ladders, fishing ladders, cloud ladders, winding ladders, folding rakes, etc.

(2) Water implements (diving and crossing equipment): anchors, swim bladders, cormorants (bamboo tubes), water paddles, water spiders, flippers, box boats, floating bridges, floating ladders, etc.

(3) Lock picking tools (lock opening and work tools): key cutters, curved blades, extension keys, small saws, scissors, nail pullers, etc.

(4) Firearms (lighting equipment and explosives): light torches, flaming arrows, smoke signals (light and sound signals), smoke screens, fire bombs, etc.

Some of these are merely copies from sources such as "Bubi-shi," and some are completely absurd and far from practical, but it is believed that by first trying out these ninja weapons for yourself and becoming proficient in a way that suits your body, you can confirm their safety and then, for the first time, be able to freely appear and disappear, and demonstrate the powers of ninjutsu.

[Ichiro Watanabe]

The decline of ninjutsu

In this way, ninjutsu evolved from a lowly art to a martial art, but the times did not encourage a resurgence of ninjutsu, and it went into a steady decline. During the Kansei Reforms (1787-1793), of the 21 Koga samurai families who petitioned the shogunate for protection and the revival of ninjutsu, about half complained that they were in financial difficulty and could not even maintain their family status.

On the other hand, from the second half of the 18th century, during the Bunka and Bunsei eras (1804-1830), ninjutsu, which had already lost its substance, began to be actively treated as a suitable subject in reading books and plays, and the elements of magic and illusion that had once been shunned in ninja books as heretical were taken up with interest, and supported by the development of directing techniques, characters such as Nikki Danjo, Jiraiya, Tenjiku Tokubei, Ishikawa Goemon, and Nezumi Kozo appeared as protagonists, and their grandiose exploits were applauded by the general audience. Intriguing ninja techniques were also performed in vaudeville halls and parlor entertainment. While in the late Edo period, ninjas were often portrayed as villains wielding mysterious and supernatural powers, the creative new ninjas such as Sarutobi Sasuke and Kirigakure Saizō, who appeared in the Tachikawa Bunko series at the end of the Meiji period, drew the masses into their superhuman, fantastical world, and were welcomed along with the large number of ninjas created by Makino Shozo and others using film trick techniques in the early Taisho period, becoming the forerunners of the so-called ninja boom that followed World War II.

[Ichiro Watanabe]

"The Secrets of Ninjutsu" by Ito Gingetsu (1917, Bukyou Sekaisha)" ▽ "The Secret Records of Ninjutsu" by Fujita Seiko (1936, Chiyoda Shoin)" ▽ "Ninjutsu" by Adachi Makiichi (1957, Heibonsha)" ▽ "Doronron" by Fujita Seiko (1958, Nihon Shuposha)" ▽ "The Secret Teachings of Ninjutsu" by Okuse Heishichirou (1959, Bonbonsha)" ▽ "Ninjutsu - Its History and Ninja" by Okuse Heishichirou (1963, Jinbutsu Oraisha) ▽ "Ninpo - Its Secret Teachings and Examples" by Okuse Heishichirou (1964, Jinbutsu Oraisha) ▽ "The Life of a Ninja" by Yamaguchi Masayuki (1961, Yusankaku) ▽ "Ninjutsu - Why do modern people admire ninjas?" by Adachi Makiichi, Ozaki Hideki, and Yamada Munemune (1964, Sanichi Shobo)" ▽ "Complete Collection of Japanese Martial Arts, Volume 4" (1966, Jinbutsu Oraisha)" ▽ "Japanese Martial Arts Series, Volume 5" (1982, Dohosha Publishing) ▽ "The Genealogy of the Ninja" by Moriyama Yu (1972, Sogensha) ▽ "Records of the Ninja Village" by Ishikawa Masatomo (1982, Suiyosha) ▽ "Modern Japanese Translation of the Bansenshukai (Yang Ninja Chapter, Yin Ninja Chapter, Nin Weapon Chapter)" (1976-81, Seishudo)

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

Japanese:

わが国武術の一つで、軍事・政治上など特別の目的をもって、敵地・敵陣にひそかに潜入し、敵方の動静や機密を探索するための術技をいう。ときに集団で暗殺・奇襲・後方攪乱(かくらん)などの直接行動に出て、敵の戦力に大きな打撃を与えたりした。一般の武術流派に比べて、流祖や伝系が明確でないものが多いが、戦国時代を通じてほぼ完成の域に達した。伊賀・甲賀・紀州（根来(ねごろ)・雑賀(さいが)）の3主流のほか、芥川(あくたがわ)流、義経(よしつね)流、福島(ふくしま)流、扶桑(ふそう)流、忍甲(にんこう)流、甲陽(こうよう)流、白雲(はくうん)流、戸隠(とがくし)流などが知られている。甲賀流14世を名のった藤田西湖(せいこ)の研究によれば、文献上にその名のみえる忍術流派は71流、そのうち伝書・資料の確認されるもの31流を数える。

［渡邉一郎］

歴史

広義の忍術の起源は、人類の生活、戦争の歴史とともに古く、中国古代の兵書『孫子(そんし)』用間篇(ようかんへん)をはじめ、作戦の展開上、間(かん)や諜(ちょう)の利用を説くものが多く、時代によって細作(さいさく)・遊偵(ゆうてい)・姦細(かんさい)、または遊士(ゆうし)・行人(こうじん)などとよばれた。わが忍術の起源についても、聖徳太子の使った志能便（しのび）に求める説があるが、実際は平安末、源平時代以後のことで、とくに南北朝の動乱期、戦闘の規模が大きくなり、集団化したため、物見(ものみ)（斥候）や間者(かんじゃ)（探偵）の使用が不可欠となった。知将といわれた楠木正成(くすのきまさしげ)は京都の動向を察知するため、伊賀者(いがもの)48名を雇い、これを3番に分け、常時16名ずつを京都に潜入させていたという。さらに応仁(おうにん)の乱（1467～77）を経て1世紀にわたる戦国時代には、諸大名間の攻防戦が激化するとともに、奪口(だっこう)、竊盗（しのび）、草（くさ）、屈（かまり）、乱波（らっぱ）、透破・素破・水波（すっぱ）など、いろいろの名でよばれた忍の者・忍術使いの活動が活発となり、技術的にも深められた。

［渡邉一郎］

忍者

これら忍びの者は、初め敵地の地理的事情に詳しい野伏(のぶし)や山盗の類を使用する場合が少なくなかったが、しだいにその任務内容が多様化し、単なる情報収集（物見）にとどまらず、敵の兵糧や武器を略奪（剛盗(ごうとう)）したり、夜間に潜入して敵陣を攪乱したり、夜襲・放火（夜討(ようち)）などの先導役などにあたらせたりしたため、いよいよ忍びの専門的技術が必要となり、火薬の使用法などに独自のくふうがなされるようになった。そして大名に召し抱えられて、特別任務を帯びて活躍するようになる。

　小田原(おだわら)の北条氏康(うじやす)に使われた風間小太郎を首領とする風魔(ふうま)一族、武田信玄(しんげん)に仕えた富田郷左衛門らの三つ者（間見(あいみ)・見分(みわけ)・目付(めつけ)）、上杉謙信(けんしん)の簷猿(のきざる)や夜盗組、毛利(もうり)家の佐田兄弟、村上家の相部(あいべ)次郎左衛門らがそれで、なかでも伊賀・甲賀地方の地侍(じざむらい)や郷士の間に伝えられた忍びの組織的・集団的技術がいよいよその存在を鮮明にしてきた。1487年（長享1）長享(ちょうきょう)の乱に、将軍足利義尚(あしかがよしひさ)が近江(おうみ)の守護代六角高頼を攻めたとき、鈎(かまり)（滋賀県栗東(りっとう)市）の陣において奇功をたてて一躍有名となり、室町から戦国期にかけて、伊賀忍者の棟梁(とうりょう)（上忍）である北の藤林長門守(ながとのかみ)、南の百地三太夫(ももちさんだゆう)および予野(よの)の服部半三(はっとりはんぞう)をはじめとして、楯岡(たておか)の伊賀崎道順(どうじゅん)、音羽(おとわ)の城戸(きど)弥左衛門、下柘植(しもつげ)の木猿(きざる)・小猿(こざる)、上野の左(ひだり)、山田の八右衛門、神戸(かんべ)の小南、神山の太郎四郎、同太郎左衛門、野村の大炊(おおい)孫太夫、新堂の小太郎など陰忍の名人を輩出した。

　越えて1581年（天正9）織田信長の伊賀進攻に、彼ら地侍層は連合してこれに対抗しようとしたが、信長の圧倒的な軍勢に敗れ、地侍の多くはその厳しい追及を逃れて、大和(やまと)・山城(やましろ)・丹波(たんば)・紀州・河内(かわち)・伊勢(いせ)などへ流散したが、やがてその技能を買われて、前田利家(としいえ)、福島正則(まさのり)などの大名に仕えて、伊賀忍術の正統を地方に伝えた。

　これより先、予野の服部氏は三河松平氏（後の徳川氏）に仕えて生国を離れていたが、1582年の本能寺の変に際し、当時泉州堺(さかい)にあった家康が窮地に陥ったとき、半三の子、半蔵正成(まさなり)は伊賀者200人、甲賀者100人の動員に成功し、家康一行を鹿伏兎(かぶと)峠越えで無事通過させ、岡崎に送り届けた。その功によって半蔵の支配下に伊賀者200人が召し抱えられた。一方、甲賀の忍者は、1600年（慶長5）関ヶ原の役の前哨(ぜんしょう)戦となった伏見(ふしみ)の籠城(ろうじょう)戦に甲賀から100余人が救援に駆けつけ、うち70余人が戦死するという目覚ましい活躍をみせた。家康はその功に報いるため、甲賀百人組を編成させ、与力格を与えた。

　近世初頭のこの段階では、忍術はいまだ弓馬剣槍(けんそう)のような近世的流派を形成するに至っていなかった。忍術としてのテクニックは現実に存在し、戦術上の必要性は大いに認められたが、それは閉鎖的な非公開の秘術であり、口伝(くでん)と体伝とによってのみ伝承され、ほとんど文字には残されてこなかったし、また倫理的な性格が希薄であり、実務は身分的に軽輩下賤(げせん)の者（下忍）が携わるもの、特務的集団の者のみが修練すべきものという認識が強かったからである。1637年（寛永14）の島原の乱に、在郷の甲賀者望月(もちづき)兵大夫ら100人が勇躍して原城攻めに参加したが、戦功をあげるには至らなかった。この出動を最後にして、中世的な忍者活動は終止符を打ち、やがては忘れられた存在となる運命にあった。

［渡邉一郎］

忍書の成立

4代将軍徳川家綱(いえつな)の時代に入ると、幕藩体制も安定期に入り、文治的風潮が強まるとともに、幕初のように隠密(おんみつ)を各地に潜行させて外様(とざま)諸藩の動向を監視する必要もほとんどなくなり、中世的な忍びの術もしだいにその存在意義を喪失し、忍者集団の栄光や誇りも年とともに薄れていき、技術を継承することも困難となった。

　このため廃絶の危機に直面した忍者集団の内部から、かつて忍びの上手たちが用いた秘密の忍技や忍器などを集録するとともに、先行諸武術と同じような体系化と理論づけを行い、近世的武芸としての忍術の地位を明らかにしようとする機運が強まった。この時期に作成された代表的な忍書としては、1655年（承応4）服部美濃守清信(みののかみきよのぶ)が、伊賀者の統領服部半蔵家に伝わる数々の伝承と忍具を中心にまとめた『忍秘伝(にんぴでん)』4巻、1676年（延宝4）伊賀の上忍藤林長門守の子孫と伝える、甲賀国境に近い湯舟(ゆふね)の藤林佐武次保武(さむじやすたけ)が集大成した『萬川集海(まんせんしゅうかい)』6篇(ぺん)22巻、および5年後の81年（延宝9）に藤一水子正武(とういっすいしまさたけ)、実は紀州藩の新楠(しんくすのき)流の兵学者名取三十郎(なとりさんじゅうろう)正武が忍術の正しいあり方について、技法および心法を中心に論述した『正忍記(しょうにんき)』3巻の三つをあげることができる。

　なかでも『萬川集海』は、伊賀・甲賀の11人の代表的な忍者の考案した忍術・忍器、および当時の諸流を比較検討し、正心(しょうしん)、将知(しょうち)、陽忍(ようにん)、陰忍(いんにん)、天時、忍器の6篇に分け、中国明(みん)代の兵書『武備志(ぶびし)』などを援用しつつ、儒教倫理を基礎に置いて、忍術全般を系統的、具体的に叙述しており、まさに伊賀・甲賀両流の正典とされるにふさわしい大著であるといえよう。正心を第一とするは、正心はすべての行動の根本であり、この業に熟達した者が邪心を抱けば、忍芸はたちまち盗賊の術に化すであろうと心法的な面を強く求めている。これは『正忍記』もまったく同じ立場で、技法よりも心法に重点を置いて叙述している。

［渡邉一郎］

忍の技法

伊賀・甲賀および紀州を中心に発生した忍の技法には、中世修験者(しゅげんじゃ)が用いた九字護身法(くじごしんほう)や山嶽(さんがく)兵法のテクニックがその背景にあると指摘されているが、前述の『正忍記』には、忍術には(1)音声忍、(2)順忍、(3)無生法忍、(4)如幻忍、(5)如影忍、(6)如焔忍、(7)如夢忍、(8)如響忍、(9)如化忍、(10)如空忍の十忍があるとし、また『萬川集海』では、忍には陽忍と陰忍とがあり、「陽忍」とは謀計の知慮（詭計(きけい)）をもって、その姿を顕(あらわ)しながら敵中に入る法、「陰忍」とは、人目を忍び姿を隠し、敵の虚隙(きょげき)を計り、「隠形(おんぎょう)」の術をなし、特別の道具や仕掛け（忍器・忍具）を使って忍び入る法をいう。この隠形とは、いわば虚実転換の法で、敵の行動に応じて虚実の位を変え、巧みに敵の目をくらまし、わが身形を隠して窮地を逃れ、敵地での隠現出没を自由にする術であるという。

　いわゆる木遁(もくとん)・火遁・土遁・金遁・水遁の五遁の術をはじめ、人・禽獣(きんじゅう)・魚・虫から日月星辰(せいしん)・雲霧・雷電・風雨などまで、すべて世の中にありとあらゆる事象を臨機に応用する。しかし、これを実行するには機敏で強靭(きょうじん)な体力と強固な精神力が要求され、心身両面における日常の錬磨、すなわち早足(さそく)・忍歩き・跳躍・登攀(とうはん)・潜水・調息(ちょうそく)・気合(きあい)などの体力の会得と、精神集中・忍耐力の養成が必要とされ、さらに夜間の潜行活動に不可欠な夜目透視・遠目・遠耳(とおみみ)などの訓練が重視されていた。忍はつねに生命の危険を伴うが、「手柄高名は無用なり、只(ただ)身命を全うして通ずること（復命）を宗(むね)とすべし、如何(いか)にも逃げ延びん」ことを本意とせよとしている。

［渡邉一郎］

服装と変装

服装は山着(やまぎ)をもととした軽快ないでたちで、夜間行動に便利な黒覆面・黒装束(しょうぞく)ばかりでなく、潜伏擬装用として、表は渋茶や柿(かき)色、裏はねずみ色に染めた。敵地への潜入の方法は、多くは夜陰に乗じて、ときに大雨や火事などを利用し、また祭礼の人出や喧嘩(けんか)・騒動などに紛れ込んだ。したがってときには変装したが、虚無僧(こむそう)・出家・山伏・商人・放下師(ほうかし)・猿楽(さるがく)・常のなりの七つを七方出の術という。また携帯用具としては、編笠(あみがさ)・かぎ縄・石筆・薬・三尺手拭(てぬぐい)・付竹(つけだけ)（発火用具）の六つを「忍の六具」といい、干鮑(ほしあわび)・するめ・梅干などの携帯食糧や、まき菱(びし)・手裏剣・針・爆薬などを懐中に忍ばせた。

［渡邉一郎］

忍具・忍器

敵方に忍び入り、偵察行動をするための道具や武器については、さまざまな工夫考案がなされ、各流派によって特別な道具や独自の仕掛けが発明され、また火薬の利用が進んで、その種類は何百を数える。『萬川集海』ではこれらを次の四つに分類している。

(1)登器（梯子・縄類）　結梯(むすびはしご)、飛梯、釣梯、雲梯、巻梯、折れ熊手など。

(2)水器（潜水・渡渉用具）　碇(いかり)、浮袋、鵜(う)（竹筒）、聞金(ききがね)、水蜘蛛(みずくも)、水掻(みずかき)、挟箱船(はさみはこぶね)、浮橋、浮梯子など。

(3)開器（開鍵・工作用具）　問外(といかき)、刃曲り、延鑰(のべかぎ)、小鋸(このこ)、鋏(はさみ)、釘抜(くぎぬき)類。

(4)火器（照明用具・火薬類）　軽松明(かるたいまつ)、火矢(ひや)、狼煙玉(のろしだま)（光玉・音玉）、煙幕(えんまく)（煙玉）、伝火(でんか)など。

　これらのなかには、『武備志』などからの引き写しや、まったく実用に縁遠い荒唐無稽(こうとうむけい)なものもあるが、これらの忍器はまず自ら適否を試み、身体にあった方法で熟達することにより、安全を確認し、初めて隠現出没を自由にし、忍術の力を発揮することができるとしている。

［渡邉一郎］

忍術の衰退

こうして忍術は下賤(げせん)の術から武術としての体裁を整えるに至ったが、時代の流れは忍術の再登場を促すことなく衰退の一途をたどったといってよい。寛政(かんせい)の改革（1787～93）当時、幕府に忍術復興について保護を陳情した甲賀郷士21家のうち、約半数は経済的窮迫で家格の維持すら困難であると訴えている。

　一方、18世紀の後半、文化・文政年間（1804～30）から、すでに実質を喪失した忍術が読本(よみほん)や演劇のうえで、格好の題材として盛んに取り扱われるようになり、かつて忍書が邪道として忌避した奇術・幻術的な要素が興味本位に取り上げられ、演出技術の発達に支えられて、仁木弾正(にっきだんじょう)をはじめ児雷也(じらいや)、天竺(てんじく)徳兵衛、石川五右衛門(ごえもん)、鼠小僧(ねずみこぞう)などが主人公に登場し、その大時代的な活躍が大衆観客の喝采(かっさい)を受けた。また興味をそそる忍びの末技が、寄席(よせ)や座敷芸として演じられたりした。幕末の彼らが、多くは変幻妖怪(ようかい)な術を操る悪玉として描かれたのに対し、明治末年「立川(たちかわ)文庫」に登場した猿飛(さるとび)佐助・霧隠(きりがくれ)才蔵らの創作的な新忍者は、超人的・空想的世界に大衆を引き入れ、さらに大正初年にかけ牧野省三らの映画のトリック手法によって生み出された多数の忍者群とともに大いに歓迎され、第二次世界大戦後のいわゆる忍者ブームの先駆となった。

［渡邉一郎］

『伊藤銀月著『忍術の極意』（1917・武侠世界社）』▽『藤田西湖著『忍術秘録』（1936・千代田書院）』▽『足立巻一著『忍術』（1957・平凡社）』▽『藤田西湖著『どろんろん』（1958・日本週報社）』▽『奥瀬平七郎著『忍術秘伝』（1959・凡凡社）』▽『奥瀬平七郎著『忍術――その歴史と忍者』（1963・人物往来社）』▽『奥瀬平七郎著『忍法――その秘伝と実例』（1964・人物往来社）』▽『山口正之著『忍者の生活』（1961・雄山閣）』▽『足立巻一・尾崎秀樹・山田宗睦著『忍法――現代人はなぜ忍者にあこがれるか』（1964・三一書房）』▽『『日本武道全集　第4巻』（1966・人物往来社）』▽『『日本武道大系　第5巻』（1982・同朋社出版）』▽『杜山悠著『忍者の系譜』（1972・創元社）』▽『石川正知著『忍の里の記録』（1982・翠楊社）』▽『『現代語訳　萬川集海（陽忍篇・陰忍篇・忍器篇）』（1976～81・誠秀堂）』