That time drunk samurai didn’t realize they were under attack
In 1560, a Japanese leader attempting to capture the capital of Kyoto lost his head and most of his men when his army got too drunk and loud to realize it was under attack by a much smaller force until the enemy had cut its way to the leader's tent.
Japanese samurai leader Imagawa Yoshimoto launched an offensive in 1560 to invade to Kyoto, leading approximately 20,000-35,000 samurai west and capturing a series of small castles on his way.
Meanwhile, Oda Nobunaga controlled a small garrison approximately 60 miles east of Kyoto, right in the path of Imagawa's massive force. While other garrisons and castles adopted a defensive posture or surrendered to Imagawa, Oda raised a small force of approximately 2,500 men, between one-twelfth and one-tenth the size of Imagawa's army, and led it east.
As the two forces marched towards one another, each made its own small stop. Oda stopped to pray at the Atsuta Shrine. The priests there would later comment on how calm the samurai leader was.
Imagawa, however, stopped to loot a few castles.
That night, Imagawa's forces got hammered and feasted as Oda took advantage of the terrain and confusion.
First, he had a small group set up false battle flags from behind a ridgeline, giving the impression that he was firmly camped for the night. Then, he led most of his men through a careful maneuver under cover of darkness and thunderstorms.
Oda's force crept close to Imagawa's camp and then attacked with its full force. The partying in the camp was so loud and the attack so sudden, that many of Imagawa's samurai failed to realize they were in a fight.
Imagawa himself is said to have stormed from his tent to yell at his men for their level of drunkenness only to be immediately attacked by a spear-wielding enemy. Imagawa cut through the spear and injured his attacker, but was tackled and beheaded by another samurai.
The battle ended a short time later as Imagawa's senior officers were cut down. Oda went on to consolidate his own power and ruled half of Japan before he was killed in 1582 by an assassin.
If you've ever seen that hilarious video about the history of Japan, Oda's story is told from 3:15 to 3:40: