Toyotomi Hideyoshi in the context of "Council of Five Elders"

Shogun (将軍, shōgun; English: /ˈʃoʊ.ɡʌn/ SHOH-gun, Japanese: [ɕoː.ɡɯɴ, -ŋɯɴ] ), officially seii taishōgun (征夷大将軍; Japanese: [seꜜi.i | tai.ɕo(ꜜ)ː.ɡɯɴ, seꜜː-, -ŋɯɴ] lit. 'Commander-in-Chief of the Expeditionary Force Against the Barbarians'), was the title of the military rulers of Japan during most of the period spanning from 1185 to 1868. Nominally appointed by the Emperor, shoguns were usually the de facto rulers of the country, except during parts of the Kamakura period and Sengoku period when the shoguns themselves were figureheads, with real power in the hands of the shikken (執権) of the Hōjō clan and kanrei (管領) of the Hosokawa clan. In addition, Taira no Kiyomori and Toyotomi Hideyoshi were leaders of the warrior class who did not hold the position of shogun, the highest office of the warrior class, yet gained the positions of daijō-daijin (太政大臣, Chancellor of the Realm) and kampaku (関白, Imperial Regent), the highest offices of the aristocratic class. As such, they ran their governments as its de facto rulers.

The office of shogun was in practice hereditary, although over the course of the history of Japan several different clans held the position. The title was originally held by military commanders during the Heian period in the eighth and ninth centuries. When Minamoto no Yoritomo gained political ascendency over Japan in 1185, the title was revived to regularize his position, making him the first shogun in the usually understood sense.

Oda Nobunaga (織田 信長; [o.da (|) no.bɯ(ꜜ).na.ɡa, -na.ŋa] ; 23 June 1534 – 21 June 1582) was a Japanese daimyō and one of the leading figures of the Sengoku and Azuchi-Momoyama periods. He was the Tenka-bito (天下人; lit. 'person under heaven') and regarded as the first "Great Unifier" of Japan. He is sometimes referred as the "Demon Daimyō" and "Demon King of the Sixth Heaven".

Nobunaga was an influential figure in Japanese history and is regarded as one of the three great unifiers of Japan, along with his retainers, Toyotomi Hideyoshi and Tokugawa Ieyasu. Nobunaga paved the way for the successful reigns of Hideyoshi and Ieyasu by consolidating power, as head of the very powerful Oda clan, through a series of wars against other daimyō beginning in the 1560s. The period when Nobunaga and Hideyoshi were in power is called the Azuchi–Momoyama period. The name "Azuchi–Momoyama" comes from the fact that Nobunaga's castle, Azuchi Castle, was located in Azuchi, Shiga; while Fushimi Castle, where Hideyoshi lived after his retirement, was located in Momoyama.

Tokugawa Ieyasu (born Matsudaira Takechiyo; January 31, 1543 – June 1, 1616) was a Japanese samurai, daimyo, and the founder and first shōgun of the Tokugawa shogunate of Japan, which ruled from 1603 until the Meiji Restoration in 1868. He was the third of the three "Great Unifiers" of Japan, along with his former lord Oda Nobunaga and fellow Oda subordinate Toyotomi Hideyoshi. The son of a minor daimyo, Ieyasu once lived as a hostage under daimyo Imagawa Yoshimoto on behalf of his father. He later succeeded as daimyo after his father's death, serving as ally, vassal, and general of the Oda clan, and building up his strength under Oda Nobunaga.

After Oda Nobunaga's death, Ieyasu was briefly a rival of Toyotomi Hideyoshi, before declaring his allegiance to Toyotomi and fighting on his behalf. Under Toyotomi, Ieyasu was relocated to the Kanto plains in eastern Japan, away from the Toyotomi power base in Osaka. He built his castle in the fishing village of Edo (now Tokyo). He became the most powerful daimyo and the most senior officer under the Toyotomi regime. Ieyasu preserved his strength during Toyotomi's failed attempts to conquer Korea. After Hideyoshi's death and the Battle of Sekigahara, Ieyasu seized power in 1600.

The Matsudaira clan (松平氏, Matsudaira-shi) was a Japanese samurai clan that descended from the Minamoto clan. It originated in and took its name from Matsudaira village, in Mikawa Province (modern-day Aichi Prefecture). During the Sengoku period, the chieftain of the main line of the Matsudaira clan, Matsudaira Motoyasu became a powerful regional daimyo under Oda Nobunaga and Toyotomi Hideyoshi and changed his name to Tokugawa Ieyasu. He subsequently seized power as the first shōgun of the Tokugawa shogunate which ruled Japan during the Edo period until the Meiji Restoration of 1868. Under the Tokugawa shogunate, many cadet branches of the clan retained the Matsudaira surname, and numerous new branches were formed in the decades after Ieyasu. Some of those branches were also of daimyō status.

After the Meiji Restoration and the abolition of the han system, the Tokugawa and Matsudaira clans became part of the new kazoku nobility.

The Honnō-ji Incident (本能寺の変, Honnō-ji no Hen) was the assassination of Japanese daimyo Oda Nobunaga at Honnō-ji, a temple in Kyoto, on 21 June 1582 (2nd day of the sixth month, Tenshō 10). 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.Nobunaga's death was avenged two weeks later when his retainer Toyotomi Hideyoshi defeated Mitsuhide in the Battle of Yamazaki, paving the way for Hideyoshi to complete the unification of Japan.

The Imjin War (Korean: 임진왜란; Hanja: 壬辰倭亂) was a series of two Japanese invasions of Korea: an initial invasion in 1592 also individually called the "Imjin War", a brief truce in 1596, and a second invasion in 1597 called the Chŏngyu War (정유재란; 丁酉再亂). The conflict ended in 1598 with the withdrawal of Japanese forces from the Korean Peninsula after a military stalemate in Korea's southern provinces.

The invasions were launched by Toyotomi Hideyoshi with the intent of conquering the Korean Peninsula and China proper, which were ruled by the Joseon and Ming dynasties, respectively. Japan quickly succeeded in occupying large portions of the Korean Peninsula, but the contribution of reinforcements by the Ming, as well as the disruption of Japanese supply fleets along the western and southern coasts by the Joseon Navy, forced the Japanese forces to withdraw from Pyongyang and the northern provinces. Afterwards, with righteous armies (Joseon civilian militias) conducting guerrilla warfare against the occupying Japanese forces and supply difficulties hampering both sides, neither force was able to mount a successful offensive or gain any additional territory, resulting in a military stalemate. The first phase of the invasion ended in 1596, and was followed afterwards by ultimately unsuccessful peace negotiations between Japan and the Ming.