The Rise of the Kamakura

It was not until 710 AD that Japan was unified as a nation under a single sovereign ruler. Prior to that point in time, the four islands that make up what is now Japan had been parceled out by individual families with no central power to unite them. After that point, however, a government was constructed of the most powerful family heads in Japan, and the seat of power was the city of Nara.    
Lands were divided up according to families by the central government, and, until the founding of the Kamakura bakufu, the only governing body in the entire nation of Japan was this central court. A bakufu is a sort of band of warriors who are all loyal to the head of a family. This central court was subsequently moved from place to place, with it eventually finding its way to the city of Kyoto by the time the Taira and the Minamoto began their respective runs for power. From 710 until 1180, the central court owned all land and leased parcels out to the heads of the wealthiest families, with those less wealthy living on other people's lands as farmers and tradesman of various types. Other sections of land were maintained by the central government itself, with these farmers and tradesman gaining permission to work on the government in exchange for the payment of taxes to the government (Mass, 1974, p. 4). These large estates, known as shoen, became to be attached to hereditary titles, with the oligopoly of the court having the only power to change the titles. The only other possessors of shoen were the various Buddhist and Shinto temples.
Over time, however, the titles of these lands spread over a larger number of families as generations of families grew apart. As this happened, power of the central court over individual areas in terms of law enforcement. As the lack of central involvement dwindled, stability of the structure on a local level dwindled proportionately. This increased lawlessness prompted the central court to grant police powers to a number of warriors who, in turn, were persuaded to continue their support of this centralized political structure (Mass, 1974, p. 6). Though most landowners were not warriors, and, likewise, most warriors were not landowners, there emerged two families of warriors in the 1100s who, because of their ancestry, were able to obtain lands. These families formed large bands of warriors who followed the leaders of the families. The Taira (leaders of the Heishi - also referred to as the Heike or the Heiji, depending on who the writer was) and the Minamoto (leaders of the Genji) were, by 1150, the primary enforcers of decisions and rulings of the central court. The Taira, because of their location nearer the capital city of Kyoto, continued to gain power, and by 1179, were nearly ready to claim control of all of Japan. The following year, however, a war broke out between the Heishi and the Genji which would change the course of Japanese history for all time (Mass, 1974, p. 7).

I wanna see maps of the regions of Kanto and Chubu-Hokuriku... 

Because of that war, lasting for four years, all aspects of land ownership and taxation were changed. In 1180, there was a shift of power in the central court that raised a cry of war from within the leader's own house. Taira Kiyomori, for reasons unknown, disinherited his own son and was about to pass his titles and lands to his grandson. According to the book Azuma Kagami (a book written by scribes from 1180 - 1185 and translated by Minoru Shinoda), it was written that on the ninth day of the fourth month of 1180, Minimoto Yorimasa arranged to meet with this disinherited Prince Mochihito. They agreed to join forces and overthrow Taira Kiyomori (Shinoda, 1960, p. 149).

I wanna see the Proclamation Translated.

These deeds committed by the Taira followed a rather violent ending to a previously profitable relationship that had been maintained by the Taira and the In for three generations. The In was the retired emperor, and, as such, had a great deal of political clout in the central court, as well as vast amounts of land. Although only a series of side notes, these events thrust Taira Kiyomori into power in Kyoto and into no one's good graces. First, it seems, was the vacancy of a certain military position being filled, by order of the central court, by Shigemori, Kiyomori's heir. The Heishi had, at the time, also formed a military alliance with the Enryakuji, a powerful temple near Kyoto. So, in retaliation for the title lost to Shiregira, the In forced the head priest of the temple to renounce himself, thus weakening the temple's ties to the Taira and forfeiting some thirty-nine parcels of land to the In (Mass, 1974, p. 20). Next, it seems, a plot against the family was discovered inside the house of Taira. Kiyomori reacted quickly, executing or sending into exile all of the conspirators. Furthermore, several interior disputes broke out within the Enryakuji, further thinning their ties to the Taira. And, to fuel Kiyomori's suspicions further, his daughter and his elder son both died within a very short period of time. Due to the condition of many of the Taira lands being held in trust for the son and daughter, the In now felt justified in seizing all such lands (Mass, 1974, p. 20).
In 1179, Taira Kiyomori gathered an army, dismissing any soldier who opposed him in any way, and took over the central court, placing In Go-Shirekawa under house-arrest and taking control of all government posts vacated by the In. Although the Taira had taken control of Kyoto and now stood highest in the government, their inability to form around themselves a new central court while maintaining ties with their own lands severely jeopardized their ability to maintain control (Mass, 1974, p. 25). This is due, it appears, to the customary position in the patron-client relationship they had had with the In until so recently. Taira Kiyomori did not have the ability to govern from a central location. Besides that, by making his move to regain control over what was happening to his family, he was forced to upset the status quo in Kyoto, ruining any chance they had had to form ruler-vassal relationships that the central court had held with the families of Japan for so long.
Because of the violent upset of the status quo, there began to form, in many circles, a great deal of resentment towards the Taira. This resentment was sufficient fuel for the Minamoto to gain power in their own territories, slowly gaining momentum. As the war waged by the Minamoto against the Taira started to spread, other areas controlled by the Taira began to suffer. Orders of conscription and requests for supplies were either ignored or rejected outright (Mass, 1974, p. 27).
Now, to understand how the Minamoto, who lived as far from Kyoto as they did, came to be such a powerful force in the war, we must retrace the way the government had been dealing with the eastern provinces. As remote as the provinces were in the east, they had been largely ignored by the central court, leaving them to fend for themselves for many generations. Over time, they had developed their own methods of police force. The Minamoto had, at several times in the past, been commissioned by the central court to perform police duties. Then, in 1160, Minamoto Yoshitomo, while involved in a military disturbance, was killed. His lands were forfeit to the jurisdiction of the central court, and his sons were placed in exile. The eldest, Yoritomo, was placed in the custody of the Hojo family (a branch of the Taira that lived in the eastern province of Izu). When Yoritomo reached the age of 30, he was permitted to marry Masaku, daughter of the Hojo.
As a result of this marriage, when the Prince Mochihito issued his call to arms in 1180, many waited to see what Yoritomo, as the senior Minamoto of that line, would do. During the next four months, Minamoto Yoritomo sent letters out to houses he thought might support him. Then, in the eighth month, he declared war. The first battle, fought on the seventeenth of the month, against the house of Kanetaka, the former imperial police (Shinoda, 1960, p. 157 - 60). In many cases, though, family loyalties had to fall where their lands required them to fall; in many cases, that meant that families who sympathized with Yoritomo had to remain loyal to whoever sat at the head of the central government, simly to maintain ownership of their lands. Others remained neutral, and still others sided with Yoritomo so that the government structure would change. During that first month of war, Yoritomo also declared that he was assuming control over all lands in the east. In the same day, to punctuate his declaration, he published a notice transferring the management of a particular parcel of land in Izu from the governor to the Mishima Shrine (Mass, 1974, p. 63). This action was in direct opposition to the central court in Kyoto. Yoritomo proceeded to either confirm or bestow land on those who offered him pledges of loyalty. He also won many larger families and bushidan (warrior bands) to his cause.
Towards the end of the first month at war, Yoritomo faced his first defeat in battle. He led an army of only 300 men against an opposing army (led by fourteen men) of some three thousand men. Yoritomo was forced to go into hiding for three weeks after the battle.
Throughout Japan, however, many bushidan, who had been staying away from the war, started committing to battles against the Taira. Though these battles diminished some of the military strength of the Taira, they did not strengthen the nation's or the court's view of the Genji (many of these independent bushidan had been calling themselves Genji as they went into battle). Since most of the Minamoto clan still recognized him as chief, Yoritomo was able to regain control of lands held branches of his clan, and he issued orders throughout Japan that the warrior bands were to desist. To enforce this order, Yoritomo created the samurai dokoro, a vassal-control bureau (Mass, 1974, p. 69).
Yoritomo then sent word to the central court that he had hopes that order could be restored to that of an earlier time, with the Genji serving the court as police officials in the east and the Taira being restored to their position as police officials in the west. It does not appear that, at the time, Yoritomo considered the Taira an enemy of his, only Kiyomori was an enemy of the central court. Not until his offers of peace had been welcomed by most of the court, and then overturned by Taira Kiyomori did he consider them his own enemies.
Though, with the failures the Taira had faced within their own ranks at maintaining order in the Chubu region (between Kyoto and the Kanto, where Yoritomo was amassing his forces), there were serious doubts raised as to whether the Taira could maintain control as police-officials. Besides these failures, there had been noted excesses in their provincial duties as police, apparently against the rights of some central-owners. And so, we see the Taira becoming the subject of an even greater criticism, this time from the central court itself.
With Yoritomo having gained control over those who claimed to be fighting under the Genji banner and committing many excesses against private individuals early in the war, and having established his own seat of power in Kamakura from which he could oversee the actions of his own police-officials, it appeared that Yoritomo might be able to better serve the interests of the central court than the Taira (Mass, 1974, p. 71). On the ninth day of the ninth month, Chiba Tsunetane sent word to Yoritomo, expressing his sympathy for his cause and his intention to bring his army to join with Yoritomo's forces. Tsunetane also recommended that Yoritomo relocate his headquarters from the present location to Kamakura (Shinoda, 1960, p. 176). By the end of the first week of the following month, Yoritomo had relocated his forces to Kamakura.
At the end of the year 1180, Taira Shigehira took in upon himself to bring his army to Nara (the old capital of Japan, and thus, the site of the oldest and most respected shrines), and burn it to the ground. This included the Buddhist temples, which Yoritomo revered (Shinoda, 1960, p. 202). It is noted many times in the Azuma Kagami that Yoritomo had gone to one Shrine or another to offer prayers for his soldiers and his family. He repeatedly gives large plots of land to various shrines all over Japan, sometimes stripping them from wealthy families to do so. That same month, a soldier, serving Fujiwara Toshitsuna (who bore no good will towards Yoritomo), had taken it upon himself to behead his master and offer it to Yoritomo as a symbol of his loyalty to the latter. As it appears, treachery (whether the former master bore Yoritomo good will or ill) is not looked upon graciously. In fact, soldiers who deserted their masters to serve another were usually rewarded by the new masters. Thus, Yoritomo had this soldier beheaded, and both heads were put on display as examples of the consequences of treachery (Shinoda, 1960, p. 203)
While Yoritomo continued to negotiate with the central court, Kosi Yoshinaka, from the Chubu region, along with Minamoto Yukiie (Yoritomo's cousin), led an army into Kyoto, chasing the Taira from the city without any fighting. These two clans began gathering spoils from the retreating Taira. Kiso Yoshinaka was made Barbarian-Conquering-Great-General (Seii-tai-shogun), only the third man in the history of Japan to receive said title. Meanwhile, Yoritomo was negotiating with the In for the lands in the east. Before long, the elimination of Yoshinaka entered the conversations, and Kamakura was made protector-city of all lands east of the capital. In the tenth month of 1183, Yoritomo received permission from the In to act on behalf of the traditional order (in other words: restore peace and power to the central court) (Mass, 1974, p. 73). This was a drastic change in policy, for the Minamoto had been branded as outlaws by the central court for over 100 years. Yoshinaka was now the target of the Genji, and Yoritomo gave his brother, Yoshitsune, command of an army with the mission of taking over Ise province. Feeling threatened, Yoshinaka tried to make peace with the Heishi. Rejected, Yoshinaka took advantage of his army's presence in Kyoto, and forced the central court to withdraw their support from Yoritomo. Within days, Yoritomo's men (we must assume) had killed Yoshinaka (Mass, 1974, p. 75).
This completed, the Genji stepped up as the new national police force. They had now come to be referred to as the bakufu. They even were prodded into filling in judicial positions because of the great number of vacancies left by the fleeing Taira, the deposed Yoshinaka, and the war-torn central court. The central court (what was left intact) issued two orders to the new bakufu: 1) destroy the Heishi; 2) suppress warrior outrages (these had, in the recent turmoil, broken out all over Japan).
On the twenty-fourth day of the third month in 1185, the Genji defeated the Heishi at the battle at Dannoura (Shinoda, 1960, p. 300 - 3).
I wanna see what Battle Record said!

References
Book References
WWW References (Warning: some of these may be outdated by the time you get there!!!)