During the Sengoku period, Okayama was held by Ukita Hideie. However, as he sided with the Western Army at the Battle of Sekigahara in 1600, he was dispossessed by the victorious Tokugawa Ieyasu and his domains given to Kobayakawa Hideaki. Kobayakawa Hideaki died without heir in 1602. In 1603, Ikeda Tadatsugu, the second son of Ikeda Terumasa of Himeji Domain was awarded Okayama with a kokudaka of 280,000 koku. This was increased in 1613 with an additional 100,000 koku. However, he died in 1615 without heir and the domain was transferred to his younger brother, Ikeda Tadao castellan of Yura Castle on Awaji Island, albeit with a reduction from 380,000 to 315.000 koku. After Ikeda Tadao's death in 1632, his heir, Ikeda Mitsunaka was regarded by the Tokugawa shogunate as being too young to be entrusted with the critically-important Okayama Castle, with its strategic location on the San'yōdō highway and reassigned him to Tottori Domain. Okayama went to his cousin, Ikeda Mitsumasa, formerly of Tottori Domain. His descendants would continue to rule Okayama until the Meiji restoration.
In 1644, Ikeda Mitsumasa was authorized to construct the Tamaigū Tōshō-gū, which was the first Tōshōgū authorized to be constructed outside of territories under direct control of the Tokugawa clan. The reason why the Ikeda clan was given such preferential treatment was because Tokuhime, the daughter of Tokugawa Ieyasu, had married Ikeda Terumasa and thus both Tadatsugu and Tadao were Ieyasu's grandsons. Ikeda Mitsumasa along with Tokugawa Mitsukuni and Hoshina Masayuki is regarded as one of the three great daimyō of the early Edo Period. In 1669, he opened the Okayama Domain Han School, the first han school to be constructed in Japan. He also opened the Shizutani School in 1670, the oldest school for commoners. He was also active in land reclamation and flood controlcivil engineering projects throughout his domain. In 1700, his son Ikeda Tsurumasa completed the Kōraku-en, one of the Three Great Gardens of Japan, along with Kenroku-en and Kairaku-en. In the Bakumatsu period, Ikeda Shigemasa, the 9th daimyō, was the ninth son of Tokugawa Nariaki and thus the younger brother of the last ShogunTokugawa Yoshinobu. He was a strong proponent of the Kōbu gattai policy of uniting the shogunate with the Imperial family; however, he was forced into retirement at the start of the Boshin War. In the immediate aftermath of the Meiji restoration, the domain was involved in the Kobe Incident of 1868, a major crisis in Franco–Japanese relations, and the first major international affairs challenge for the fledgling Meiji government. In 1871, with the abolition of the han system, the domain became part of Okayama Prefecture. then Ikeda clan was ennobled with the kazoku peerage title of marquis in 1884.
Holdings at the end of the Edo period
As with most domains in the han system, Tottori Domain consisted of several discontinuous territories calculated to provide the assigned kokudaka, based on periodic cadastral surveys and projected agricultural yields, g.[4][5]
In 1672, Ikeda Mitsumasa gave 25,000 koku of new rice lands in Asakuchi and Kuboya Districts, Bitchū Province, to his second son, Ikeda Masamoto, and established a cadet branch of the clan. A jin'ya was established in what is now then Kamagata neighborhood of the city of Asakuchi, Okayama; however, its nominal daimyō lived within the jōkamachi of Okayama. The domain existed primarily as "insurance" to prevent attainder of the parent domain should the ruling daimyō die without a successor. Throughout its history, it was known as Okayama Shinden Domain (岡山新田藩), becoming "Kamogata Domain" only after the Meiji restoration.
Ikusaka Domain
In 1672, Ikeda Mitsumasa gave 15,000 koku of new rice lands in Kuboya District, Bitchū Province, to his third son, Ikeda Terutoshi, and established a cadet branch of the clan. It existed as a "paper domain" throughout most of the Edo period with its revenues coming from the treasury of the parent domain, and its nominal daimyō lived within the jōkamachi of Okayama. Domain administration was non-existent, with officials dispatched from Okayama Domain in charge of domain affairs. The domain existed primarily as "insurance" to prevent attainder of the parent domain should the ruling daimyō die without a successor. Throughout its history, it was known as Okayama Shinden Domain (岡山新田藩), becoming "Ikusaka Domain" only after the Meiji restoration.
Genealogy (simplified; Ikeda clan – Okayama)
Ikeda Tsuneoki (1536–1584)
Terumasa, 1st daimyō of Himeji (1565–1613)
Toshitaka, 2nd daimyō of Himeji (1584–1616)
I. Mitsumasa, 1st daimyō of Okayama (2nd creation. cr. 1632) (1609–1682; r. 1632–1672)
II. Tsunamasa, 2nd daimyō of Okayama (2nd creation) (1638–1714; r. 1672–1714)
III. Tsugumasa, 3rd daimyō of Okayama (2nd creation) (1702–1776; r. 1714–1752)
IV. Munemasa, 4th daimyō of Okayama (2nd creation) (1727–1764; r. 1752–1764)
V. Harumasa, 5th daimyō of Okayama (2nd creation) (1750–1819; r. 1764–1794)
VI. Narimasa, 6th daimyō of Okayama (2nd creation) (1773–1833; r. 1794–1829)
Sagara Nagahiro, 12th daimyō of Hitoyoshi (1752–1813)
Sagara Yorinori, 13th daimyō of Hitoyoshi (1774–1856)
Sagara Yoriyuki, 14th daimyō of Hitoyoshi (1798–1850)
X. Akimasa, 10th daimyō of Okayama (2nd creation) 1st Marquess (1836–1903; r. 1868–1869, Governor of Okayama: 1869–1871, Marquess: 1884)
Norimasa, 13th family head and 2nd Marquess (1865–1909; 11th family head and 2nd Marquess: 1903–1909)
Tadamasa, 14th family head and 3rd Marquess (1895–1920; 12th family head and 3rd Marquess: 1909–1920).
Nobumasa, 15th family head and 4th Marquess (1904–1988; 13th family head and 4th Marquess: 1920–1947, 13th family head: 1947–1988)
Takamasa, 16th family head (1926–2012; 14th family head: 1988–2012). m. Princess Atsuko of the Imperial House of Japan (b. 1931). No issue; the family became extinct after his death.
I. Tadatsugu, 1st daimyō of Okayama (1st creation. cr. 1603) (1599–1615; r. 1603–1615)
II. Tadakatsu, 2nd daimyō of Okayama (1st creation) (1602–1632; r. 1615–1632)
III. Mitsunaka, 3rd daimyō of Okayama (1st creation), 1st daimyō of Tottori (3rd creation) (1630–1693; r. 1632)
Nakazumi, 1st daimyō of Tottori-Shinden (1650–1722)
Yoshiyasu, 3rd daimyō of Tottori (3rd creation) (1687–1739)
Muneyasu, 4th daimyō of Tottori (3rd creation) (1717–1747)
Shigenobu, 5th daimyō of Tottori (3rd creation) (1746–1783)
Harumichi, 6th daimyō of Tottori (3rd creation) (1768–1798)
Iyohime Chikako (1792–1824) m. Shimazu Narioki, 10th daimyō of Satsuma (1791–1859)
VII. Naritoshi, 7th daimyō of Okayama (2nd creation) (1811–1842; r. 1829–1842)
Motosuke (1559–1584)
Yoshiyuki (1577–1618)
Yoshinari (1605–1676)
Yoshitaka (1641–1696)
Yoshimichi (1681–1743)
Masamichi, 3rd daimyō of Kamogata (1714–1792)
Masanao, 5th daimyō of Kamogata (1746–1818)
Masami, 6th daimyō of Kamogata (1772–1819)
Masayoshi, 8th daimyō of Kamogata (1811–1847)
Utako (1830–1877) m. VIII. Yoshimasa, 8th daimyō of Okayama (2nd creation) (1823–1893; r. 1842–1863. Son of the 5th daimyō of Nakatsu.)
Hisako (1848-1868) m. IX. Mochimasa, 9th daimyō of Okayama (2nd creation) (1839–1899; r. 1863–1868. Son of Tokugawa Nariaki, daimyō of Mito.)
