1. Heian Period 794 – 1180. The imperial court is located in Heian (modern Kyoto). The period features the rise of the samurai warrior class. The ideal of the samurai of pre-bafuku Japan was of a highly-cultured servant of the imperial court, a necessary evil dedicated to upholding imperial tradition. The political power of the imperial court was based on urbanization; rural Japan was wild and dangerous, and samurai were needed to contain it. As samurai clans began to harness the economic and military potential of rural Japan, the days of a relatively powerless, independent imperial court were numbered. With the evolution of two dominant families of competing samurai, the Taira and the Minamoto, each boasting royal blood (of different lines), the path to civil war was set.
2. Gempei War 1180-1185. The Minamoto, nearly exterminated a generation before, rise up and ultimately crush the Taira. After the Minamoto gain the upper hand on land in 1183 at Kurikara, the most significant battles are combined land/sea operations that result in the destruction of the Taira at Dan-no-Ura in 1185. The Gempei War, however, is just as much about the internecine struggles among the Minamoto as it is a war between the clans.
3. Kamakura Period 1192 – 1335. The period of the Minamoto bakufu; the rule of the Minamoto themselves was cut short by the early death of Yoritomo (in 1199), so the actual power passed to his wife’s family, the Hojo. The period is often referred to as the Hojo Regency (both the emperor and the shogun were Hojo puppets).
4. Mongol Invasions 1274 and 1281. The Mongol invasions marked a dramatic change in the nature of samurai warfare. The stylized and ritualistic warfare of the Japanese was tested by the tactical and technical superiority of the Mongols. Combat on land – especially in 1274 – demonstrated the seriousness of the Mongol threat. Fortunately for the Japanese, the Mongols were improbably defeated twice by severe storms that ruined their fleet (a.k.a. the divine wind or kami-kaze).
5. Muromachi Period 1336 - 1576

It goes well beyond the purposes of this short note to describe Heian culture and politics. The Gempei War finished a process that turned around the traditional relationship between the imperial court and its military servants. The Taira built their political power by marrying daughters to imperial relatives. The military and economic power of the Taira and the Minamoto were founded on large land holdings outside of the capital, the Taira in the west, the Minamoto the east. In addition, the Taira were traders and sailors and dominated the China trade. It is felt here that the Minamoto built a broader base of manpower in the east that could not be offset by the Taira currying favor with the imperial family; the ranks of the Minamoto samurai were filled out with rougher provincial warriors who were not expected to rise to the Heian standards of the Taira courtiers.

The war started in April, 1180, with the aging Minamoto no Yorimasa (a distant relative of the titular head of the clan, Minamoto no Yoritomo) declaring rebellion with Prince Mochihito against the emperor and his Taira supporters. The Minamoto were badly organized for war, so the timing of this declaration is puzzling; their poor showing over the next year is no surprise. The Battle of Uji saw a small Minamoto detachment fleeing Kyoto with Mochihito defeated by a much later force of Taira (see Rodney Tompson’s piece in the most recent Slingshot, reference below). Yorimasa committed a legendary suicide in wake of his defeat.

Seeing he had little choice, Minamoto no Yoritomo declared for war, but he was badly defeated at the battle of Ishibashiyama, wherein his small force was brutally crushed by overwhelming Taira numbers in a preemptive strike (not much of the traditional dueling between samurai champions in this one).

Having narrowly the Taira noose, Yoritomo (whose singular talent lay in escaping close calls), fled east to his base around Kamakura, and began to consolidate his forces, building a sizable army before the end of 1180. In November, the Minamoto army confronted the Taira at Fujigawa. The Minamoto won a surprising "victory" as the Taira mysteriously panicked because of the whirring wings of a flock of water fowl coming off of the nearby marshes (by legend this was mistaken for the arrival of a flanking force of Minamoto cavalry).

The years 1181 and 1182 were relatively quiet, as the sides gathered strength and jockeyed for position, but operations were curtailed because of draught, poor harvests and famine. Disaster struck the Taira in the form of the plague, which decimated the ranks of their supporters and carried away their leader and best general, Taira no Kiyomori. The latter was succeeded as the head of the clan by Taira no Munemori, an incompetant who lacked the confidence of the family(who doubted his Taira petigree).

The Minamoto were less affected by the plague in their stronghold in the east.

By the time the war got hot again in 1183, the Taira had suffered irreplaceable losses to plague and famine, and the Minamoto numbers would prove to be decisive. The Taira were defeated at the Kurikara pass, and thereafter fought three major losing holding actions/defensive battles, Ichinotani, Yashima, and Dan no Ura. The main drama after Kurikara concerns the deadly struggles between the Minamoto brothers (Yoritomo, Yoshitsune and Noriyori) and their cousin (Kiso Yoshinaka) for clan superiority. Only Yoritomo, the nominal head of the clan, survived the war or its immediate aftermath.

The most colorful figures of the Gempei War are the Minamoto cousin, Kiso Yoshinaka and his consort (gozen), Tomoe, the legendary samurai. Yoshinaka was already emerging as a rival to Yoritomo before his great victory at Kurikara. Afterwards, the full resources of the Minamoto were directed at defeating Yoshinaka. Among Yoshinaka’s commanders was his uncle Minamoto no Yoshiee, whose loyalties appear to have shifted between the cousins; it is believed his secret reports to Yoritomo finally brought about Yoshinaka’s downfall via treachery, but that comes later. At this time a Minamoto drive on Kyoto was in full swing under Yoshinaka’s command.

The Taira command had devolved upon Taira no Koremori, the least able of Taira generals, being the son of Munemori and the buffoon who had fled before the geese at Fugjigawa. He was seconded by Taira no Michimori, another weak link. Their army was comprised of a core force of high quality samurai, poorly supported due to losses to famine and the plague. The list below basically has two components, good quality samurai and large number of poor foot (with limited upgrades available).

The Battle of Kurikara Pass was an example of a clever tactician baiting and beating the plodder. The outnumbered Taira took up a very strong position in the pass, leaving their enemy apparently little choice but a frontal attack. Yoshinaka hit upon a wily scheme to pin the Taira in place via the traditional dueling and skirmishing of samurai warfare – all very controlled and ritualistic, and appealing to Taira vanity, while sneaking a flanking force in behind them. Cattle with flaming torches on their horns were employed to panic the Taira (clearly a superstitious lot), thus stampeding them out of their excellent position in the pass and down into a killing field in the valley below, where the Minamoto inflicted very heavy casualties.

Gempei War 1180-1185

Introduction
Outline of Medieval Japanese History
Lists
Figures and References