was a samurai member of the Minamoto clan

Minamoto clan

was one of the surnames bestowed by the Emperors of Japan upon members of the imperial family who were demoted into the ranks of the nobility. The practice was most prevalent during the Heian Period , although its last occurrence was during the Sengoku Era. The Taira were another such offshoot of...

, who fought in the Hōgen

Hogen Rebellion

The was a short civil war fought in order to resolve a dispute about Japanese Imperial succession. The dispute was also about the degree of control exercised by the Fujiwara clan who had become hereditary Imperial regents during the Heian period....

 and Heiji Rebellion

Heiji Rebellion

The was a short civil war fought in order to resolve a dispute about political power. The Heiji no ran encompassed clashes between rival subjects of the cloistered Emperor Go-Shirakawa of Japan in 1159. It was preceded by the Hōgen Rebellion in 1156...

s and in the Genpei War

Genpei War

The was a conflict between the Taira and Minamoto clans during the late-Heian period of Japan. It resulted in the fall of the Taira clan and the establishment of the Kamakura shogunate under Minamoto Yoritomo in 1192....

. He was the adopted son of Minamoto no Tameyoshi

Minamoto no Tameyoshi

was head of the Minamoto samurai clan during his lifetime, and grandson of Minamoto no Yoshiie; he led the Minamoto in the Hōgen Rebellion. Tameyoshi is also known as ....

 since age thirteen.

Sasaki fought under Minamoto no Yoshitomo

Minamoto no Yoshitomo

was the head of the Minamoto clan and a general of the late Heian period of Japanese history. His son Minamoto no Yoritomo became shogun and founded the Kamakura Shogunate, the first shogunate in the history of Japan.-Hōgen Rebellion:...

 in the Hōgen Rebellion (1156), aiding in the siege of the Shirakawa palace

Siege of Shirakawa-den

The siege of the Shirakawa-den was the central event of the Hōgen Rebellion, a succession dispute which broke out after the death of the cloistered Emperor Toba...

. Three years later, he fought for the Minamoto again in the Heiji Rebellion, incurring the ire of the rival Taira clan

Taira clan

The was a major Japanese clan of samurai in historical Japan.In reference to Japanese history, along with Minamoto, Taira was a hereditary clan name bestowed by the emperors of the Heian Period to certain ex-members of the imperial family when they became subjects...

.

By the time of the Genpei War, the all-out civil war between the Minamoto and the Taira, Hideyoshi had lost his hereditary estate in Ōmi Province

Omi Province

is an old province of Japan, which today comprises Shiga Prefecture. It was one of the provinces that made up the Tōsandō circuit. It is nicknamed as .Lake Biwa, Japan's largest lake, is located at the center of the province...

 as a result of the displeasure of the Taira. He set out to appeal to his uncle, Fujiwara no Hidehira

Fujiwara no Hidehira

was the third ruler of Northern Fujiwara in Mutsu Province, Japan, the grandson of Fujiwara no Kiyohira. During the Genpei War, he controlled his territory independently of the central government; however, he was the official imperial governor for Mutsu Province as of 1181. He offered shelter to...

, for aid, but stopped in Sagami province

Sagami Province

was an old province in the area that is today the central and western Kanagawa prefecture. It was sometimes called . Sagami bordered on Izu, Musashi, Suruga provinces; and had access to the Pacific Ocean through Sagami Bay...

 along his way. There, he attracted the interest of a daimyo named Shibuya Shigekuni; Hideyoshi married Shibuya's daughter, and became heir to that land. His sons would serve Minamoto no Yoritomo

Minamoto no Yoritomo

was the founder and the first shogun of the Kamakura Shogunate of Japan. He ruled from 1192 until 1199.-Early life and exile :Yoritomo was the third son of Minamoto no Yoshitomo, heir of the Minamoto clan, and his official wife, a daughter of Fujiwara no Suenori, who was a member of the...

, the first Kamakura shogun

Kamakura shogunate

The Kamakura shogunate was a military dictatorship in Japan headed by the shoguns from 1185 to 1333. It was based in Kamakura. The Kamakura period draws its name from the capital of the shogunate...

.