Izuna-gongen (also pronounced as Iizuna-gongen) is a syncretized god of Shintoism and Buddhism which is said to originate from a belief in the mountains of Mt. Izuna in Minochi County, Shinano Province (now Nagano Prefecture). In many cases it is expressed as a Karasu Tengu (crow-billed goblin) riding a white fox with a sword and rope. Sometimes snakes wind around its whole body or the white fox. Generally it is enshrined as a god of victory, and used to be believed by warlords in the Middle Age including Yoshimitsu ASHIKAGA, Kenshin UESUGI, and Shingen TAKEDA. It is especially famous that the ornament in front of the helmet of Kenshin UESUGI was a statue of Izuna-gongen.
More specifically, it is an illustration of tactics using fire in which one ties the legs of a bird on the back of a fox and set fire to the wings and send them to the castle of enemy. It also holds a memorial service for those foxes and birds which brought victory. The success of these tactics depend on whether one can grow the fox small in a dark place (such foxes are called Kudagitsune, mythological pipe fox) and send them into a narrow and dark part of the enemy's castle with a burning bird on their backs.
Meanwhile 'Izuna Tactics' initiated by Izuna-gongen came to be regarded as an improper tactic along with 'Atago Tactics' and 'Dakini Tenpo Tactics.'
While it was regarded as an abnormal tactic that used tengu (a mountain spirit, portrayed as winged and having a long nose) and foxes, it penetrated as a popular belief
These tactics were described as follows. 'There is an improper tactic called Izuna no Jutsu which confuses human eyes.' ("Bosou Manroku")
Burn powder incense of shikimi (Japanese star anis) for the Buddha as well as in the world.'
When one uses Izuna tactics, he will not be blamed for his improper tactics if he burns this powder incense.' ("Yamato Honzo")
Nevertheless this god is earnestly believed especially in the Kanto region and the north including Izuna-jinja Shrine in Shinshu and Takaosan Yakuo-in Temple on Mt. Takao (Takao-cho, Hachioji City, Tokyo Prefecture), apart from regions with vulgar beliefs. It is called Izuna-gongen or Izuna-myojin.
Belief in Izuna-gongen is described slightly differently between each engi (writing about the history) and saimon (address to the gods).
An oldest reference whose creation date is known is found in "Togakushiyama Kenko-ji ruki, narabini jo" (around Muromachi Era) and it describes as follows;
I am the third tengu in Japan.'
I wish to serve on the side of this mountain, and escape from the three kinds of heat with gracious wind from (Kuzuryu) Gongen (incarnation).'
I should be raised to the gyokudai (jewel pedestal) of jinshi.'
I shall be Chinju (local Shinto deity) of this mountain.'
"Togakushiyama Kenko-ji ruki, narabini jo" is an engi which refers mainly to the origin in Togakushi, and describes how Izuna-myojin becomes a guardian bestowing gracious winds from Togakushi Gongen to illustrate the secondary position of Izuna-myojin.
On the other hand in "Izunayama Ryakuengi" during the Edo period, Izunadaimyojin is referred to as 'it worships Otonoji no mikoto, the fifth child of Tenjin, and its honji (original ground or true nature) is Dainichi Nyorai (Mahavairocana) '
It turned to Jizo Bosatsu and Shogun Jizo etc. and after an academic practitioner visited Mt. Izuna and saw Izuna-myojin in April 848, in 1233, castellan of Ogino-jo Castle ITO Buzennokami Tadatsuna, the originator of Sennichi-dayu, worshipped Izuna-myojin after a 400 year blank and raised the 'Thirteen Oaths.'
In "Izuna-koshiki," it is stated that the third of ten princes who did not become priest and stayed laity among eighteen princes of Myozengekko and Konpira-yasha was Izuna-chira-tengu, who is Izuna-myojin of Mt. Izuna. This statement is relevant to the above-mentioned "Togakushiyama Kenko-ji ruki, narabini jo."
Shugen related to Mt. Izuna is called 'Izuna Shugen,' and a practitioner, known as Sennichi-dayu, served as a leader for generations. In early-modern times Nishina clan served as Sennichi-dayu and ruled 100 koku (1 koku is about 180 liters; an old unit of volume) of Izuna shinryo estate. It is likely that the Izuna belief at Mt. Izuna was formed in later ages around this Sennichi-dayu.
Though it is not clear as to when Izuna-gongen became complete as a belief, the statue of Izuna with the existing oldest signature is that of Eifuku-ji Temple dating back to 1406. The color painting on silk of Izuna-gongen deposited by Okayama Prefectural Museum is presumed to have been created in the Muromachi period, and the name Takuzen of the period of the Northern and Southern Courts (Japan) to Muromachi is found on Izuna-mandara-zu transmitted at Rinno-ji Temple on Mt. Nikko. In addition, Izuna-gongen of Yakuo-in Yuki-ji Temple on Mt. Takao inspired Shungen, Chuko no So (father of restoration), entered the monastery in Eiwa era (1375-79), indicating that Shungen had already received information on Izuna-gongen. Taking into consideration the descriptions including engi and Izuna-koshiki, it can be assumed that a systematic Izuna belief was already formed in the beginning of the Middle Ages.
Izuna belief has many varieties, ranging from belief in devils and tengu, to beliefs among warlords, practitioners, and ninja (professional spy in feudal Japan highly trained in stealth and secrecy), to beliefs in foxes, which are complicated aspects of the belief. Though we have to wait accumulation of researches in the future on the realities, it seems it was partly regarded as a magic or improper tactics already in Muromachi period.