Born in 1550 (though his origins are disputed among sources), Tsugaru Tamenobu became the adopted heir of the Oura clan in 1567, inheriting the position of a local lord under the Nanbu clan based at Oura Castle. On 5 May 1571, he launched his bid for independence with a bold double strike: a surprise attack that captured Ishikawa Castle, defended by senior Nanbu retainer Ishikawa Takanobu, followed the same day by a three-pronged assault that took Watoku Castle. He went on to capture Daikoji Castle (1575-76), Namioka Castle (1578), and Aburakawa Castle and the surrounding Sotogahama coast (1585), bringing nearly all three districts of Tsugaru under his control. In 1590 he attended Toyotomi Hideyoshi's Odawara campaign and had his domain confirmed as an independent daimyo, no longer subordinate to the Nanbu. He sided with the Eastern army at the Battle of Sekigahara in 1600 and became the first lord of the Tsugaru (Hirosaki) domain. He died in Kyoto in 1608 at age 58.

An ambitious figure who rose from the status of a minor Nanbu-clan vassal through sheer force of will. Renowned for his tactical acumen in surprise attacks and stratagems — famously capturing two castles in a single day — he also displayed sharp political instincts, racing to Toyotomi Hideyoshi's court ahead of his former overlords the Nanbu to secure recognition as an independent daimyo.

The Tsugaru domain that Tamenobu founded endured throughout the Edo period, and Hirosaki Castle and its castle town remain the heart of the Tsugaru region today. As the architect of Tsugaru's independence from Nanbu rule, he left his mark on numerous castle ruins and historic sites across present-day Aomori Prefecture.