Sengoku period

The Sengoku period (戦国時代, lit. "Warring States period") was a historical period in Japanese history that was marked by near-constant civil war between individual clans, social upheaval, and political intrigue from 1467 until 1603. The Sengoku period was initiated by the Ōnin War in 1467 which brought instability and chaos across Japan as well as the long-term deterioration of the Ashikaga shogunate.

Even before the conflict began, the shogunate was heavily decentralized and already failed to win the favor of many daimyō who lived in domains far from the capital of Kyoto and began to fight uncontrollably with each other over land and influence. Japan also suffered from earthquakes and famines at the beginning of the 14th century, which led to peasant uprisings against the Ashikaga clan. The final straw was a succession crisis within the Ashikaga shogunate over the birth of Ashikaga Yoshimasa's son Ashikaga Yoshihisa, which created friction with Yoshimasa's younger brother Ashikaga Yoshimi and his wife Hino Tomiko. It also directly led to the Ōnin War between the Hosokawa and Yamana clans, a conflict that quickly spread to the rest of Japan.

The Sengoku period saw the rise and fall of numerous daimyō, most notably the "Three Great Unifiers"—Tokugawa Ieyasu, Oda Nobunaga, and Toyotomi Hideyoshi—and other figures such as Ōtomo Sōrin, Date Masamune, and Imagawa Yoshimoto. It also saw the arrival of Portuguese traders in the island of Tanegashima in 1543, the first time that Japan had established full contact with the Western world. Soon Japan would become the next battleground in the Assassin-Templar War, as the Assassins and Templars would later establish a foothold in the country. Prior to its discovery by Europeans, Japan had no previously-known presence of Assassins or Templars, or the existence of any branches affiliated with the Hidden Ones or the Order of the Ancients. For the Templars, this newly discovered land was an opportunity to spread their ideology of a New World Order to millions of new minds after a series of defeats in Europe. Thus, the Templars assigned the Jesuit priests Francis Xavier, Alessandro Valignano, and Francisco Cabral to spread Tempar doctrine under the guise of converting the Japanese to Christianity.

Seeking to counter this, the Assassins found allies in the ninja of the Iga and Koga provinces, from whom they learned new techniques to their already-proficient repertoire of stealth abilities. Some daimyō would cast their lot with the Assassins, such as Ieyasu and Nobunaga, while others like Uesugi Kenshin would willingly join the Templars in spite of their ties to foreign institutions like the Catholic Church. While most ninjas such as Hattori Hanzō became Assassins, some like Mochizuki Chiyome became Templars. Hanzō in particular would become a prolific figure in the Sengoku period, as he carried out the assassinations of Mori Motonari, Takeda Shingen, and Kenshin, all of whom were rival daimyō that posed a threat to his vassal Nobunaga and later Ieyasu.

By 1573, Nobunaga eliminated the last vestiges of the Ashikaga shogunate after he overthrew his personal puppet Ashikaga Yoshiaki. By this point, the Sword of Eden came into the possession of Lord Nobunaga after Hanzō had assassinated Shingen during the Battle of Mikatagahara. He also reneged on his promise of an alliance with the Assassins and decided to pursue his goal of reunifying Japan under the banner of the Oda clan, independent of the Brotherhood. This sudden betrayal greatly angered the Assassins, who decided to retrieve the Sword of Eden from Nobunaga. In 1582, the Assassins learned that one of Nobunaga's generals, Akechi Mitsuhide, planned to betray him. In response, Hanzō tasked monk Yamauchi Taka to travel to Honno-ji, kill Nobunaga, and take the Sword of Eden. Taka killed Nobunaga during Mitsuhide's attack and brought the Sword to Liu Yan, a member of the Chinese Brotherhood, who took it to her homeland.

After the death of Oda Nobunaga, his vassal Toyotomi Hideyoshi became his successor and continued his master's goal of unifying Japan. Unfortunately for Hideyoshi, he befell the same fate as Nobunaga, as he was killed by Yamauchi Taka in 1598, the same year that the Imjin War had ended in a Chinese-Korean victory over the Japanese.

With Nobunaga and Hideyoshi dead and Hanzō having been killed by rival ninja Fūma Kotarō, it fell to Ieyasu to unite the country and end to the constant in-fighting that racked Japan. In 1600, Ieyasu successfully crushed the forces of Hideyoshi's vassal Ishida Mitsunari in the Battle of Sekigahara, a major turning point in Japanese history. Three years later, he would establish the Tokugawa shogunate, which would rule Japan for over 250 years.