The was fought in 1582 in Yamazaki, Japan, located in current-day Kyoto Prefecture. This battle is sometimes referred to as the Battle of Mt. Tennō (天王山の戦い Tennō-zan no tatakai). In the Honnō-ji Incident, Akechi Mitsuhide, a retainer of Oda Nobunaga, attacked Nobunaga as he rested in Honnō-ji, and forced him to commit seppuku. Mitsuhide then took over Nobunaga's power and authority around the Kyoto area. Thirteen days later, Oda's forces under Toyotomi Hideyoshi met Mitsuhide at Yamazaki and defeated him, avenging his lord (Nobunaga) and taking Nobunaga's authority and power for himself. Background Honnō-ji Incident When Nobunaga died, Hideyoshi was busy fighting the Mōri clan in the Siege of Takamatsu. After betraying and defeating Nobunaga at Honnō-ji, Mitsuhide sent a letter to the Mōri. The letter contained a request for an alliance to crush Hideyoshi, but the letter's messenger was intercepted by Hideyoshi's forces and the plot was revealed. Great Chugoku retreat Upon hearing news that Nobunaga had been killed, and that Akechi Mitsuhide had taken command of his possessions, Hashiba Hideyoshi immediately negotiated a peace treaty with the Mōri by demanding the seppuku of Shimizu Muneharu from Takamatsu, and remained careful to keep Nobunaga's death a secret. Once the treaty was secured, on 25 June, Hideyoshi's forces retreated from Chugoku region and he led his troops on a forced march towards Kyoto, covering up to 40 km a day, spending the night at his Himeji Castle, and reaching Amagasaki on 29 June. Niwa Nagahide and Oda Nobutaka joined him as he passed through Osaka. Prelude Akechi Mitsuhide controlled two castles (Shōryūji and Yodo) in the Yamazaki region. Learning of the size of Hideyoshi's army and not wanting to be caught inside a castle with his force divided, Mitsuhide resolved to prepare for battle somewhere to the south. Due to its position between a river and a mountain, Yamazaki provided Mitsuhide with choke points that could ease the number of enemies his forces would have to face at any one time. Meanwhile, Hideyoshi decided that a wooded area called Mount Tennōzan, just outside the town of Yamazaki, was key to strategic control of the road to Kyoto. He sent a detachment under Nakagawa Kiyohide to secure this area, while he led the majority of the army to Yamazaki himself. His forces took over the mountain and gained a significant advantage. Mitsuhide arranged his army behind a small river (the Enmyōji-gawa),