The Gempei war in Japan was fought in the 12th century in Japan. It was a time of the 'cloistered emperors'. At this time the ruling emperor was usually a cypher and or a child. The adult emperors who had given up the throne carried the real power in their kimono. Sometimes you had up to three emperors at one time vying for control of the government. The Fujiwara family was also deep into the power struggle by being the emperors highest servants and also marrying into the royal family. The war starts because a cloistered emperor brought into the mix the two most powerful military families in Japan, the Taira and the Minamoto, thinking to use these families just as every other piece had been used in the power struggle. The plan backfires on the imperials, and ushers in the age of the Shogun. For the next 600-plus years, the emperor becomes a nonentity while the Shogun rules Japan.
The DLC for this game, Sengoku Jidai, is an attempt to bring the battles of the two families out of the mist of history, and onto your computer screen. The DLC takes place roughly four hundred years earlier than the battles in Sengoku Jidai. This is a time when the Samurai was much more of an archer than a swordsman, and the tales of the warriors of these times represent that fact.
Due to the mist that is present in Japanese history in the 12th century, we know of some battles and what warlord died and when. What we do not have is actual lists to be able to make out OOBs for the different battles of the Gempei War. So the decision was made by Byzantine Games to not falsify history and make some OOBs up. Instead, the DLC is based solely on skirmish mode in the game without any historical battles. It is an unfortunate but correct decision based on the records.
There has been some discussion on the web about the choice of the names of the two sides in the war. The Minamoto are listed as anti-imperials, while the Taira are listed as pro-imperials. I understand that while it is not technically correct; both were pro themselves and anti everyone else. You are still able to kick some 12th century Minamoto butt with your Taira troops, so it all works out in the end.
Minamoto no Yoritomo is the strongman who set up the shogunate after the crushing defeat of the Taira at the sea battle of Dan-No-Ura. He then consolidated his position by the hounding and then murder of his half brother Minamoto no Yoshitsune. Yoshitsune was a greatly revered swordsman whose battle with the monk Benkei, and their companionship and travels after the fight, loom large in Japanese folklore.
Sengoku Jidai is a game for anyone interested in the history of Japan. This DLC makes it more interesting with the new units and different strategies needed to win with your 12th century armies. Please see my review of Sengoku Jidai: http://www.awargamersneedfulthings.co.uk/2016/05/sengoku-jidai-review.html
Game : Sengoku Jidai DLC: Gempei Kassen
Developer: Byzantine Games
Publisher: Slitherine Games
Steam Release Date: 9/8/2016
Review Date: 10/1/2016