It was a lawless era in Japan, with petty feudal lords fighting a never-ending series of small wars over land and power. In the chaotic Sengoku period (1467-1598), the peasants often ended up as cannon-fodder or incidental victims of the samurai wars; some commoners, however, organized themselves to defend their own homes, and to take advantage of the constant warfare. We call them the yamabushi or ninja.
The key ninja strongholds were the mountainous provinces of Iga and Koga, located in what are now Mie and Shiga Prefectures, respectively, in southern Honshu. Residents of these two provinces gathered information and practiced their own techniques of espionage, medicine, warfare, and assassination.
Politically and socially, the ninja provinces were independent, self-governing, and democratic - they were ruled by town council, rather than by a central authority or daimyo. To the autocratic nobles of other regions, this form of government was anathema. Warlord Oda Nobunaga (1534 - 82) remarked, "They make no distinction between high and low, rich and poor… Such behavior is a mystery to me, for they go so far as to make light of rank, and have no respect for high ranking officials." He would soon bring these ninja lands to heel.
Nobunaga embarked on a campaign to reunify central Japan under his authority. Although he did not live to see it, his efforts began the process that would end the Sengoku, and usher in 250 years of peace under the Tokugawa Shogunate.
Nobunaga sent his son, Oda Nobuo, to take over the province of Ise in 1576. The former daimyo's family, the Kitabatakes, rose up, but Nobua's army crushed them. The surviving Kitabatake family members sought refuge in Iga with one of the Oda clan's major foes, the Mori clan.
Oda Nobuo Humiliated
Nobuo decided to deal with the Mori/Kitabatake threat by seizing Iga Province. He first took Maruyama Castle early in 1579 and began to fortify it; however, the Iga officials knew exactly what he was doing, because many of their ninja had taken construction jobs at the castle. Armed with this intelligence, the Iga commanders attacked Maruyama one night and burned it to the ground.
Humiliated and furious, Oda Nobuo decided to attack Iga immediately in an all-out assault. His ten to twelve thousand warriors launched a three-pronged attack over the major mountain passes in eastern Iga in September 1579. They converged on Iseji village, where the 4,000 to 5,000 Iga warriors lay in wait.
As soon as Nobuo's forces had entered the valley, Iga fighters attacked from the front, while other forces cut off the passes to block the Oda army's retreat. From the cover, the Iga ninja shot Nobuo's warriors with firearms and bows, then closed to finish them off with swords and spears. Fog and rain descended, leaving the Oda samurai bewildered. Nobuo's army disintegrated - some killed by friendly fire, some committing seppuku, and thousands falling to the Iga forces. As historian Stephen Turnbull points out, this was "one of the most dramatic triumphs of unconventional warfare over traditional samurai tactics in the whole of Japanese history."
Oda Nobuo escaped the slaughter but was roundly chastised by his father for the fiasco. Nobunaga noted that his son has failed to hire any ninja of his own to spy out the enemy's position and strength. "Get shinobi (ninja)… This one action alone will gain you a victory."
Revenge of the Oda Clan
On October 1, 1581, Oda Nobunaga led about 40,000 warriors in an attack on Iga province, which was defended by approximately 4,000 ninja and other Iga warriors. Nobunaga's massive army attacked from the west, east, and north, in five separate columns. In what must have been a bitter pill for Iga to swallow, many of the Koga ninja came into the battle on Nobunaga's side. Nobunaga had taken his own advice about recruiting ninja assistance.
The Iga ninja army held a hill-top fort, surrounded by earthworks, and they defended it desperately. Faced with overwhelming numbers, however, the ninja surrendered their fort. Nobunaga's troops unleashed a massacre on the residents of Iga, although some hundreds escaped. The ninja stronghold of Iga was crushed.
Aftermath of the Iga Revolt
In the aftermath, the Oda clan and later scholars called this series of encounters the "Iga Revolt" or the Iga No Run. Although the surviving ninja from Iga scattered across Japan, taking their knowledge and techniques with them, the defeat at Iga signaled the end of ninja independence.
A number of the survivors made their way to the domain of Tokugawa Ieyasu, a rival of Nobunaga's, who welcomed them. Little did they know that Ieyasu and his descendants would stamp out all opposition, and usher in a centuries-long era of peace that would make ninja skills obsolete.
The Koga ninja did play a role in several later battles, including the Battle of Sekigahara in 1600, and the Siege of Osaka in 1614. The last known action that employed Koga ninja was the Shimabara Rebellion of 1637-38, in which ninja spies aided the shogun Tokugawa Iemitsu in putting down Christian rebels. However, the age of the democratic and independent ninja provinces ended in 1581, when Nobunaga put down the Iga Revolt.
Man, John. Ninja: 1,000 Years of the Shadow Warrior, New York: HarperCollins, 2013.
Turnbull, Stephen. Ninja, AD 1460-1650, Oxford: Osprey Publishing, 2003.
Turnbull, Stephen. Warriors of Medieval Japan, Oxford: Osprey Publishing, 2011.