The Legendary Ninja Battle of the Tensei-Iga War

The mist parted, swirling through the leaves. Oda Nobuo paused to stare into the thick woods around him. Only the ragged breathing of his men disturbed the silence. Something isn’t right. He watched, the thought still half-formed, as hundreds of fletched arrows whistled through the mist to impale the shocked warriors around him. Nobuo’s disastrous defeat haunted his dreams for many years. A traditional stronghold of ninjutsu practitioners, the Iga province proved too formidable an opponent for the young general.

Oda Nobuo, acting on his father’s orders, first attempted to obtain a foothold into the province of Iga by capturing and fortifying Maruyama Castle. Unfortunately, the Iga ninjas had already infiltrated his workforce and, armed with foreknowledge that Nobuo planned to eventually subdue the whole province, they decided to burn the castle to the ground in a night raid. The act enraged Nobuo and he immediately sought retribution through a full-scale invasion. After dividing his army into three columns to traverse the steep mountain passes surrounding the Iga province, roughly 12,000 of his warriors converged on the village of Iseji.

Unfortunately for Nobuo, roughly 5,000 Iga ninja had prepared for his arrival. The Iga waited until Nobou entered the valley near Iseji and then sprung their trap. Volleys of arrows hammered down into the weary samurai and foot soldiers, felling great numbers. Iga spearmen and swordsmen took advantage of the surprise to carve bloody paths through the confused enemies. News quickly reached Nobuo that the Iga had also occupied the passes behind him, cutting off his retreat. As the direness of the situation circulated through the men, the army quickly began to disintegrate; commanders committed seppuku, samurai died of friendly fire, and fleeing foot soldiers became lost in the foggy woods. Rain poured from the heavens and turned the valley into a muddy quagmire as the shadows lengthened into evening. Yet still, the Iga ninjas continue their slaughter.

At last, their thirst for blood slacked, the Iga allowed the defeated enemy to escape. Nobou survived and returned to his father in humiliation. Although the famous battle proved unconventional warfare could prevail against a numerically superior enemy, the Oda clan would not be denied their victory for long. Soon afterwards Nobou’s father, Oda Nobunaga himself, would lead an army nearly four times the size of the first invasion force to attack the Iga province once again. Aided by ninjas of the Koga, Nobunaga would crush the Iga resistance. The surrender of the final Iga outpost led to a brutal massacre. Although the surviving Iga ninjas that managed to flee the province continued to practice and spread ninjutsu, the Iga would never again raise to prominence.

The Iga ninjas had, for a time, thwarted the incursions of one of the most powerful clans in Japan. Exceptional training and the intelligent use of their environment allowed the Iga warriors to overcome their considerable numerical inferiority. Their victory on the battlefield would help build a reputation as one of the most feared mercenary units in Japan.