Aizu (会津) was once a han of Japan and a somewhat reoccurring domain in Rurouni Kenshin. Much of its ties to the series lie within its notable allegiance to the Tokugawa Shogunate and reputable samurai that served in the Bakumatsu.
About Aizu
Aizu was a powerful domain during the Edo period. During the early years of the Edo Period, its retainers, the Hoshina Clan, came to a meteoric rise in power after having established a strong alliance with the Tokugawa Shougante upon adopting the illegitimate son of Tokugawa Hidetada, Hoshina Masayuki, and was bestowed the right to use the surname of Matsudaira upon this deed, becoming a branch of the Tokugawa Clan.
Historically, the region was renowned for its many aspects even for its far and remote location from Edo. During the peace of the Edo period, Aizu soon flourished as a major center of power, commerce, and cultural tradition; the city of koya storehouses of Kitakata was said to have been the produce reserve stronghold of the Shogunate and the Imperial Household, to the han itself being known as Japan's Treasure House of Food, as the region was said to have started massive agriculture campaigns, including reinvigorating the soil for the increased production of rice and enriching the treatment of farmers by its daimyo that spread throughout Northern Japan, and was a major center of production of goods born of this campaign.
Its most significant aspect however, would go to its fame of samurai and martial prowess. Due to the influences of the Tokugawa Shogunate and the reach of western ideas, samurai education was reinforced by the establishment of the Nisshinkan, considered one of the Three Famous Martial Academies of the Edo period, while the dynamic history of the Sengoku period saw the region flourish martial arts like nowhere else in Japan, opening many schools within the castle city of Aizuwakamatsu and drawing in the many wandering samurai that sought to improve themselves. This even includes the region being the birthplace of the legendary Hiten Mitsurugi-ryū created by Hiko Seijūrō of Kitakata, whose claim to fame was said to be established upon singlehandedly felling the belligerent and warring han of Nagumo. Regarding its military, Aizu's forces were the most deployed, from the enforcement and security of the nation, and were considered the most professional in their manners of conduct. Such campaigns were that of the patrol of Northern Japan, including Hokkaidō to the islands of Sakhalin, and to the security operations throughout Edo Bay upon the arrival of Commodore Perry and the threat of his Black Ships. Finally, Aizu's professionalism was further reinforced upon setting rules of warfare and conduct upon the 1790s for its forces, including codifying human rights and protecting non combatants in times of war; it should be noted that these treaties of conduct historically came about nearly 70 years before the known Geneva Convention.
Bakumatsu
During the end of the Edo Period and at start of the Bakumatsu, Aizu ultimately sided with the bakufu, even though its current damiyo, Matsudaira Katamori, desired negotiations with both sides of the conflict along with influence from Isshi Shishi member Sakamoto Ryoma, and for peaceful negotiations amongst Western powers. Despite this, they resisted the Imperial army's advances with its own significant and famous military force with Katamori also supporting the rise of the Shinsengumi upon their requests to legally patrol Kyoto during his years as Kyoto Shugoshoku, for the purpose of security in the Japanese capitol. Saitō Hajime of the Shinsengumi was also one of the prominent commanders of its forces.
Some of its prominent warriors were Takimi Shigure, and Gentatsu Takatsuki. Both of them were notable samurai; Gentatsu himself was also infamously renowned as a Hitokiri. As Saigo Takamori of Satsuma allegedly hired Aizu samurai to prevent the Kinmon Incident, his mutiny to the Tokugawa was divulged. Both of them became head leaders in the discovery of that secret negotiation between him and major influential head individuals of the Isshin Shishi, and were to stage a most crucial attack that could have ultimately dealt a most devastating blow to the imperial resistance; much to their dismay, Hitokiri Battosai was also present and was the demise of Hitokiri Gentatsu along with the complete failure of the assault.
Boshin War - Battle of Aizu and Disaster
At the end of the Bakumatsu's turbulence, the now Satsuma and Chōshū controlled court upon the resignation of the Tokugawa Shogunate nevertheless saw Aizu as a prominent enemy for its actions. Though Matsudaira pleaded forgiveness, the unforgiving nature of the early Sat-Cho controlled court lead him to wage the early battles of the Boshin War - and its resistance against the newly formed Meiji Government lead to the Aizu War.
Though Aizu was called "The Guardian of Kyoto", its forces were eventually overwhelmed and its castle city of Aizuwakamatsu was forced to use all of its civilians in combat against the Ishin Shishi, even after everything but Tsuruga Castle itself had been decimated. Unable to compete with more modern weaponry, Aizu surrendered to the Imperial army on September 22, 1868, and suffered devastating losses, with many its citizens having committed seppuku or having been the victims of war.
Soon after, the Meiji Government got rid of Aizu Prefecture, and held resentment against its remnants and survivors for its position as an enemy of the empire during the war. Much of their harsh punishing involved banishing its surviving samurai to exile to the northern prefecture of Tonami, to even cruel humiliation, forbidding even the burial and contact of war casualties in the domain for six months.
Although Saitō Hajime survived the battle, he was taken as a prisoner of war going by the name of Ichinose Denpachi. He was later released for good behavior. After his release he was forced to into hiding and would go by the name of Fujita Goro name given by Matsudaira Katamori after the end of the Boshin War.
The Takani family of Aizu were famous for their generational devotion to medicine as well as their advanced skills. During the Battle of Aizu, it was unknown what became of them during the chaos that swept the castle city of Aizuwakamatsu; it is said that only their youngest daughter, Takani Megumi, is their only known living survivor.