Hereditary lords · The Kamakura house and its housemen · as at first light, 1 January 1200

Date house (Isa Tomomune)

The Date are the best-known example of how Kamakura planted its men in the north.

Isa Tomomune, a Hitachi houseman, was given the Date district of southern Mutsu in 1189, and his family took its name from it. Their seat is in the Fukushima basin, on the road to Shirakawa and the south and on the way to Taga and Hiraizumi; the lordship is a stewardship held of Kamakura, not a province. By the page's genealogy the founder died in 1199 and his son Munemura, then twenty-six, leads the house in 1200.

The family is a mid-sized one in 1200: its great days are in the sixteenth century, which is not the concern of this game.

Who he is

Name
Isa Tomomune, called Date Tomomune; his son Munemura is the heir
Title
Steward (jitō) of the Date district of Mutsu; houseman from Isa in Hitachi
Since
Granted the Date district of Mutsu in 1189 (English Wikipedia: Date clan)
Born
Tomomune 1129 to 1199 (the page's genealogy); Munemura 1173 to 1251 (same list)
Family
The family came from the Isa district of Hitachi and claims descent from Fujiwara no Uona (the page's sixteen generations); the genealogy lists Munemura (1173 to 1251), Yoshihiro (1185 to 1256) and later heads. If the genealogy's date is right, Tomomune died in 1199 and Munemura heads the house on 1 January 1200.
Confidence
medium

English Wikipedia (Date clan). The page says Yoritomo gave Date to Tomomune in 1189 for his help in the Genpei war and against Yoshitsune, and that the seat moved to Sendai in 1601 (far later).

Overlord

Minamoto no Yoriie; the Ōshū commissioner in the north

What it holds

  • The Date district of Mutsu, a stewardship (jitō)

How it was acquired

Granted in 1189 (English Wikipedia).

Allies and rivals

Allied with the Ōshū commissioner's circle; neighbours: the Yūki at Shirakawa (recalled), the Hitachi houses.

How things stand that morning

Settled. A new family on the old Emishi border.

Wealth

The rice and mulberry of the Fukushima basin; the Ōshū road; no figure.

Military

Date housemen; no numbers.

Threats

  • Old Ōshū retainers
  • Kamakura's own changes of steward

Where the sources disagree

  • The English page gives the founder as Isa Tomomune; the form 'Nakamura Tomomune' that some sources use is not on the page. The page also says the Date clan 'originated in Shimōsa', which does not match its Hitachi origin; the page does not reconcile the two.

Evidence: One English page.

On the map: District only.

Primary sources for Kamakura regime

Chronicles, registers, sagas and inscriptions written in or near 1200 that cover this entry. Each has its own page with editions, translations and where to read it.

  • Hundred Times Refined Extracts: court annals (late thirteenth century, from court diaries). Short dated annals of the imperial court excerpted from courtiers' diaries, among them the Gyokuyo and the Meigetsuki. Read online
  • Mirror of the East, Anonymous; compiled by officials of the Kamakura shogunate (compiled about 1300 from the shogunate's records, diaries and family documents). The Kamakura house's own chronicle, in daily entries. Read online
  • Jottings of a Fool: an interpretative history of Japan, Jien (慈円) (about 1219 to 1220, revised to about 1223). A history by Kujo Kanezane's brother, head of the Tendai school and the leading churchman of the court, written to explain the fall of the Kujo and the rise of the warriors as the working of principle (dori). Read online
  • Diary of the Inokuma Regent: the diary of Konoe Iezane, Konoe Iezane (近衛家実) (1197 to 1218, as a daily diary). The diary of the regent's heir, aged twenty-one in 1200 and already a senior courtier under his father Konoe Motomichi, who was regent (sessho) for the child emperor Tsuchimikado. Read online
  • Leaves of Jade: the diary of Kujo Kanezane, Kujo (Fujiwara) Kanezane (九條兼實) (1164 to 1200, as a daily diary). The diary of the former regent, Yoritomo's ally at court, who had been driven from power in the Kenkyu purge of 1196 and lived in retirement in 1200. Read online
  • Record of the Bright Moon: the diary of Fujiwara no Teika, Fujiwara no Teika (藤原定家) (1180 to 1235, as a daily diary, with gaps). The diary of the poet and courtier, then thirty-eight and a middle-ranking official of the Kujo house. Read online
  • Surviving Documents of the Kamakura Period, Various; collected by Takeuchi Rizo (竹内理三) (documents of 1185 to 1333, collected and printed 1971 to 1997). The collected charters, deeds, court orders, shogunal directives, temple records and land registers of the Kamakura age, printed in date order. Read online
  • The Tale of the Heike, Anonymous; traditionally attributed to Shinano no Zenji Yukinaga, performed and reshaped by blind reciters (early thirteenth century in its first form; the standard Kakuichi text was fixed in 1371). The epic of the Genpei war, in the form the reciters gave it over the century after 1200. Read online

Sources and studies

  1. KJA_BRIEF.md and the OMNIA board for sheet kja (the lead's notes: [own] computation, [not yet checked against the source] recollection, [en] English Wikipedia)
  2. Azuma Kagami (the Kamakura chronicle), Kenkyu 10 to Shoji 2 entries, recalled and through the brief; ja.wikipedia and ja.wikisource were refused in this session, so no entry was re-read
  3. Jeffrey P. Mass, Warrior Government in Early Medieval Japan (1974), from memory; the archive.org full text could not be opened
  4. English Wikipedia: Date clan (read this session; thin)

Last revised 4 November 2026. Published 4 November 2026. Suggest a correction on the OMNIA Discord.