The term ‘Ninja’ is a western one. In Japan, these bands of covert operatives were known as ‘Shinobi‘ from the Japanese to “to steal away’ or ‘to hide.” The shinobi or Ninja may have originated in China, as their mode of operation was similar to that of Chinese assassins described by Sun Tzu in his ‘Art of War. However, they did not begin to appear in the Japanese historical record until the twelfth century AD.
Some historians such as Stephen Turnbull maintain that the Ninja were recruited from the lower classes or rejected samurai. However, most elite Ninja groups were raised and trained in families. These families lived in independent territories, they ruled without an overlord. The Iga and Koga areas of Japan were renown for their Ninja ‘training schools’ and soon gave their names to the two most prestigious groups of Ninja: the Iga and Koga.
At these schools, Ninja trained in the art of Ninjutsu, which equipped them with stealth as well as fighting techniques. Ninja needed to learn how to camouflage themselves in different environments and move swiftly and quietly. To this end, their arsenal of equipment was diverse. As well as weapons such as darts, spikes throwing stars chains, poison, swords- even hand grenades, they used ropes, hooks, a particular listening device called a mizugumo and the happo, a small eggshell filled with a blinding powder to aid swift exits.
The Ninja enjoyed their heyday in the Sengoku period of the fifteenth and seventeenth centuries when they became indispensable to Japanese ruling clans vying with each other for supremacy. Ninja carried out the secret tasks the honorable samurai would not. One example of Ninja activities came from the Shimabara Rebellion of 1637-1638 when the Shogun Tokugawa Lemitsu hired Koga Ninja to infiltrate Christian rebels in Hara castle, Hizen province. The Koga assassins were sent into the castle every night to report on weak spots, also raiding the castle’s provisions and sabotaging the defenses.
Ninja also carried out covert killings. Those at risk from a Ninja assassination began to take precautions, hiding weapons in bathrooms and under floorboards so some attempt could be made to protect themselves. Houses and castles were modified to incorporate anti ninja devices: traps and trip wires, as well as deliberately squeaky floorboards and noisy gravel paths, to warn of the ninja’s approach.
In the late sixteenth century, the warlord Oda Nobunaga curtailed Ninja activities. However, in the eighteenth century, the Ninja became respectable again, forming the core of the fledgling Japanese secret service.