The Tsugaru clan sided with
Tokugawa Ieyasu during the
Battle of Sekigahara in 1600, although Tsugaru Tamenobu's eldest son, Nobutake, was serving
Toyotomi Hideyori as a page in
Osaka Castle. After the Tokugawa victory at Sekigahara, the Tsugaru clan remained somewhat “suspect” in the eyes of the fledgling
Tokugawa shogunate as Tsugaru Tamenobu granted refuge to
Ishida Mitsunari’s son and arranged for Ishida Mitsunari's daughter to marry his third son and heir,
Tsugaru Nobuhira. As a result, the clan was confirmed in its original territory with only a nominal increase in
kokudaka to 47,000
koku. Tsugaru Tamenobu further fueled concerns by reconstructing
Hirosaki Castle on a massive scale disproportionate to the size of his territories. The early years of the Edo era were marked by a series of major
O-Ie Sōdō disturbances over the succession to the clan chieftainship. Tsugaru Nobuhira's accession was disputed by supporters of the son of Tsugaru Nobutake in the of 1607. Further troubles arose in the of 1612, the of 1634, and the of 1647. Tsugaru Nobuhira was forced to reduce his wife to concubine status and marry a niece of Tokugawa Ieyasu to strength his political ties to the shogunate. However, he named the son by his first wife,
Tsugaru Nobuyoshi as heir. His son by the niece of Tokugawa Ieyasu was made head of a subsidiary
hatamoto household based in
Kuroishi. Nobuyoshi was forced to retire in 1655 for alleged misgovernment, and was replaced by his son,
Tsugaru Nobumasa, who was a reformer who developed the resources of the domain. Nobumasa's son
Tsugaru Nobuhisa developed the arts and cultural level of the domain, but was beset by numerous natural disasters, including bad weather and repeated eruptions of
Mount Iwaki. He continued to rule from behind-the scenes during the tenure of his grandson,
Tsugaru Nobuaki and great-grandson
Tsugaru Nobuyasu as the domain fell further and further into debt. Nobuyasu's son,
Tsugaru Nobuakira attempted reforms, but was vexed by corrupt officials and died under suspicious circumstances in 1791 without heir.
Tsugaru Yasuchika, son of the 5th Lord of Kuroishi, was appointed
daimyō of Hirosaki to succeed Nobuakira. Under his tenure, the official
kokudaka of the domain was raised from 47,000 to 70,000 and then to 100,000
koku to cover the expenses of dispatching military forces to
Ezo to protect Japan's northern borders. Also under Yasuchika's tenure, Kuroishi was raised in status to become
Kuroishi Domain, In 1821, during his
sankin kōtai journey to
Edo, he survived an assassination attempt by Sōma Daisaku, a former retainer of the Nanbu clan. Although Yasuchika was a noted reformer who attempted to strength the domain, he spent a tremendous amount of money attempting to arrange prestigious marriages for his incompetent son,
Tsugaru Nobuyuki, which again plunged the domain into financial crisis. Nobuyuki was eventually forced out of office in 1839 and a complete outsider, the 7th son of
rōjū Matsudaira Nobuakira, lord of
Yoshida Domain in
Mikawa Province was adopted into the Tsugaru clan as
Tsugaru Yukitsugu. Yukitsugu managed to restore order and prosperity to the domain and modernized its military forces through increased implementation of
rangaku studies. ==In the Boshin War==