One of the first of the samurai to use his position for his own ends, Taira Masakado rebelled against the imperial court at Heian (Kyoto) and even proclaimed himself emperor.

Taira Masakado, as his name suggests, came from the prestigious Taira clan and was descended from the emperor Kammu who reigned over a hundred years before his birth. In Masakado's time in the early 10th century the samurai class had not yet dominated the nobles at the imperial court. They were nevertheless wealthy landowners who were periodically called to Kyoto to perform guard duty or for a military purpose, such as destroying rebels and bandits. Their followers formed a bushidan or warrior band which consisted of other samurai (often relatives or friends) and their retainers. Many bushidan would then make up the samurai armies of this time and naturally the more successful the commander the more warriors would want to join him and share the glory. Masakado's bushidan hailed from the Toyota and Sashima districts of Shimosa province and were tied to him through mutual dependence and security.

After serving the imperial regent Fujiwara Tadahira in his youth, Masakado returned to the fertile plain called the Kanto, where Tokyo now stands, to wage war on his rivals; a war against the government for its refusal to grant him the post of kebiishi, which was something similar to being head of the national police. Although he won a victory in 935 at Kawawa he was defeated twice the following year and one source puts one of those defeats down to the wrath of the gods. Yet he was undaunted and took the side of a corrupt district official called Okiyo Okimi who was caught in a dispute and went about raiding and burning government buildings. Masakado even went so far as to assert his imperial blood and proclaim himself New Emperor or shinno and set up his own court to reflect this status. Governors were appointed to rule the eight Kanto provinces as Masakado declared his independence. 

The Kyoto government sent two samurai to quell Masakado's rebellion: Taira Sadamori (who was an old enemy) and Fujiwara Hidesanto. But the conflict was worsened when some of Masakado's soldiers raped Sadamori's wife and the ensuing fighting at Kawaguchi in 940 was fierce which ended in his defeat. The final battle happened two weeks later at Kitayama (or Kojima) in Shimosa province. Sadamori entered in force and proceeded to burn the houses of Masakado's supporters as well as Masakado's opulent mansion he had built to befit his status as the new emperor. The opposing armies met behind a line of temporary wooden shields in order to deter mounted charges. But the wind was quite strong and rendered these walls ineffective. The cavalry from both sides ordered an advance and just when combat was joined the horse of Taira Masakado was pierced by an arrow and he perished not long afterwards. Fujiwara Hidesanto apparently killed him and took his head to Kyoto.

Further Reading

Early Samurai (Osprey Publishing) - Anthony J Bryant.

Samurai Commanders 1 (Osprey Publishing) - Stephen Turnbull.