Nobunaga was on the verge of unifying the country, but died in the unexpected rebellion of his vassal Akechi Mitsuhide. Nobunaga only had a few guards and retainers with him when he was attacked, ending his Sengoku period campaign to unify Japan under his power. Mitsuhide's motive for assassinating Nobunaga is unknown, though there are multiple theories for his betrayal. By , Oda Nobunaga was the most powerful daimyo in Japan and was continuing a sustained campaign of unification in the face of the ongoing political upheaval that characterized Japanese history during the Sengoku period.
The death of Uesugi Kenshin left the Uesugi clan devastated also by an internal conflict between his two adopted sons, weaker than before.
The nearly decade-long Ishiyama Hongan-ji War also had already ended with the conclusion of peace. It was at this point that Nobunaga began sending his generals aggressively in all directions to continue his military expansion. Nobunaga, confident of unifying the country after destroying the Takeda clan, returned to Azuchi in high spirits. Nobunaga immediately ordered Akechi Mitsuhide to go to the Chugoku region to support Hideyoshi, and he himself was to follow soon after.
Having dispatched most of his soldiers to take part in various campaigns, only a small force was left to protect his person and there was little fear that anyone would dare strike Nobunaga; security measures were weak.
Taking advantage of this opening, Mitsuhide suddenly turned against his master. Upon receiving the order, Mitsuhide returned to Sakamoto Castle and moved to his base in Tanba Province. He engaged in a session of renga with several prominent poets, using the opportunity to make clear his intentions of rising against Nobunaga. Mitsuhide led his army toward Kyoto under the pretense of following the order of Nobunaga. It was not the first time that Nobunaga had demonstrated his modernized and well-equipped troops in Kyoto, so the march toward Kyoto of Mitsuhide's men did not raise any suspicion.
