Counts · Other imperial lands · as at first light, 1 January 1200

Diez

An old comital house of the Lahn round Diez, below Limburg, which had taken the Niederlahngau county from the Konradiner in the 10th century.

The brothers Gerhard II and Heinrich III rule jointly: their county runs along the Lahn to below Weilburg, north into the Westerwald and east into the Goldener Grund; they hold the advocacy of Kastel opposite Mainz and lands in the Wetterau. The Weilnau branch the assignment asks about does not yet exist as a line: Heinrich III founds it from 1208 at Altweilnau.

Who he is

Name
Gerhard II (count 1189-1223) and his brother Heinrich III (1189-1234), ruling jointly
Title
Counts of Diez
Since
1189, the death of their father Heinrich II
Born
not pinned
Family
Sons of Heinrich II (count 1145-1189), Frederick I's companion on his Italian campaigns, who had inherited Wetterau lands, probably from an heiress of the counts of Nürings. Heinrich III will found the Weilnau line from 1208 (Altweilnau first named 1208); on 1 January 1200 there is no separate Weilnau county. Gerhard II later sits on the council of the young King Henry (VII).
Confidence
high

de.wikipedia Grafschaft Diez.

Overlord

The king (county and high courts) and various churches; fief links not given in the sources reached.

What it holds

  • Diez castle and the county on the Lahn
  • The high courts of Stuhllinden (Höhn), St Maximinus at Ellar and Reckenforst (Dietkirchen) (named in later sources; not dated to 1200)
  • The Goldener Grund to the east (Camberg area)
  • The advocacy over Kastel opposite Mainz (given to Philip in 1207 for royal land at Usingen)
  • Wetterau lands from a Nürings heiress (detail not pinned)
  • Weilnau: not yet a castle or line (Altweilnau first named 1208)

How it was acquired

County inherited; the Wetterau lands by Heinrich II's marriage or inheritance from the Nürings (not pinned).

Allies and rivals

Neighbours and rivals of Nassau, the Limburg advocates and Katzenelnbogen; the Isenburgers inherit Limburg about 1219.

How things stand that morning

The brothers hold Diez undisturbed. Their side in the throne war on 1 January 1200 is not pinned; by 1207 they deal with Philip (Kastel for Usingen), and the house's later court service is Staufen.

Wealth

Lahn valley farmland, courts and tolls (not pinned), the Kastel advocacy at the Mainz bridgehead.

Military

Diez castle; vassals not pinned.

Threats

  • Nassau's rise on the Lahn
  • The Mainz schism touching Kastel

What the year holds

What happened next, if nothing in play changes it. Each event carries what it depends on and what would stop it.

  1. 1200No dated event found; the Weilnau division is of 1208.

Places of note

  • Diez castle: Seat of the counts.
  • Kastel (Mainz-Kastel): Advocacy held by Diez until 1207.

Where the sources disagree

  • The assignment lists Weilnau as a separate lord: on 1 January 1200 Weilnau is not yet a line (de.wikipedia: Heinrich III founds it from 1208; Altweilnau first named 1208). Covered here.

Evidence: Holders and joint rule well attested; the extent of the county in 1200 is from later court districts.

On the map: Drawn from later court districts; the Westerwald and Wetterau holdings are not drawn.

Primary sources for Empire

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.

8 more in the sources library for The Rhineland, the Low Countries and the Swiss Lands.

Sources and studies

  1. Grafschaft Diez, de.wikipedia

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