Established in 1392, the Amako were relatively minor family of Izumo Province and served the Kyogoku family at the time of the Ônin War. Tsunehisa would secure their status as daimyo and ruled from his headquarters at Gassan-Toda Castle [月山富田城].
Tsunehisa was born in March 1458, the eldest son of Amako Kiyosada (d.1478, 尼子清定), guardian of Gassan-Toda Castle from around 1467, and at first a retainer of Kyogoku Masatsune [京極政経]. He was expelled along with his father from Gassan-Toda in 1484 and was forced to wander while he gained the support of Yamanaka Katsushige [山中勝重] and other Amako allies. Gassan-Toda meanwhile came into the possession of the Enya family. During a New Year's celebration in 1486 Tsunehisa snuck a handful of men into Gassan-Toda and killed the lord of the castle and his family, thus reclaiming the place as his own. Under Tsunehisa's leadership the Amako clan became powerful in Izumo and came into conflict with the Ôuchi clan|, taking advantage of the latter's preoccuptation with events in Kyoto to expand their power. In October of 1518 (Eisho 15/9/6; a less likely tradition holds that this event occured in 1513), as the Amako were moving against Hoki Province, the Amako vassal Sakurai Soteki [桜井宗的] rebelled and was besieged by Tsunehisa's eldest son, Masahisa, who was shot and killed by a defending archer. Tsunehisa was overcome by grief and thought of retiring in favor his brother Hisayuki, giving up the notion when Hisayuki refused to consider it. Tsunehisa would later name Masahisa's son, Akihisa, as his heir. Tsunehisa entered Aki Province and made Môri Motonari a vassal. In 1523 Tsunehisa attempted to bring down Kagamiyama Castle [鏡山城], held by Kurata Fusanobu [蔵田房信]. Fusanobu resisted strongly and it was owing to the strategms of Motonari that he was killed and the castle taken. However, within the next few years the Ôuchi reasserted their power in Aki Province and Mori Motonari turned from the Amako and reentered their camp.
When Tsunehisa's great rival, Ôuchi Yoshioki, died in 1528, Tsuenhisa took the opportunity to expand Amako influence eastward and into Iwami, always an area of contention for its valuable silver mines. In 1532 his 3rd son Okihisa (? – 1534)was encouraged by his retainers to rebel over the issue of the Amako succession. Okihisa's troops were defeated by an army led by Tsunehisa's bother, Haruyuki. Okihisa afterwards committed suicide. Soon after, Tsunehisa retired in favor of his grandson Akihisa (Haruhisa) but continued to make most important decisions. During this period, the Amako captured the Iwami silver mines [石見銀山] in 1537 and then lost them to the Ôuchi temporarily in 1539 (the Amako would reclaim them two years later.) He died on 1541/11/30 (Tenbun 10/11/13). His remaining son Amako Kunihisa [1492-1554; 尼子国久] remained a pillar of the Amako house for some years.
A noted strategist and competent ruler overshadowed by later warlords, Tsunehisa left as his legacy the Kitsugi Grand Shrine in Izumo, which he had built in the 1530's.
- Initial text from Samurai-Archives.com FWSeal & CEWest, 2005