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Wilhelm VI, Landgrave of Hesse-Cassel (May 23, 1629 – July 16, 1663), known as Wilhelm the Just, was Landgrave of Hesse-Cassel from 1637 to 1663.

Wilhelm VI, Landgrave of Hesse Cassel

History of the Landgravite

Landgrave was a noble title used in the Holy Roman Empire, and later on in its former territories. The German titles of Landgraf, Markgraf (“margrave”), and Pfalzgraf (“count palatine”) are in the same class of ranks as Herzog (“duke”) and above the rank of a Graf (“count”).

The Landgraviate of Hesse-Cassel was founded by Wilhelm IV the Wise, the eldest son of Philipp I. On his father’s death in 1567, the Landgraviate of Hesse was divided into four parts. Wilhelm IV received about half of the territory, with Cassel as his capital. Hesse-Cassel expanded in 1604 when Moritz, Landgrave of Hesse-Cassel inherited the Landgraviate of Hesse-Marburg from his childless uncle, Ludwig IV, Landgrave of Hesse-Marburg (1537–1604). The other sons received the Landgraviate of Hesse-Marburg, the Landgraviate of Hesse-Rheinfels and the Landgraviate of Hesse-Darmstadt.

Wilhelm V of Hesse-Cassel, father of Wilhelm VI.

The reign of the Landgrave William IX (1743-1821) (the great-great grandson of Landgrave Wilhelm VI) was an important epoch in the history of Hesse-Cassel. Ascending the throne in 1785, he took part in the War of the First Coalition against French First Republic a few years later, but in 1795 the Peace of Basel was signed. In 1801 he lost his possessions on the left bank of the Rhine, but in 1803 he was compensated for these losses with some former French territory round Mainz, and at the same time he was raised to the dignity of Prince-elector Wilhelm I of Hesse, (the territorial designation of Cassel was dropped) a title he retained even after the dissolution of the Holy Roman Empire.

Upon 1806 dissolution of the Holy Roman Empire and the dispossession of his Elector Wilhelm I of Hesse, Landgrave Ludwig X of Hesse-Darmstadt and joined the Napoleonic Confederation of the Rhine and took the title of Grand Duke Ludwig I of Hesse. At the Congress of Vienna in 1814/15, Ludwig had to give up his Westphalian territories, but was compensated with the district of Rheinhessen, with his capital Mainz on the left bank of the Rhine. Because of this addition, he amended his title to Grand Duke Ludwig I of Hesse and by Rhine.

Amalie-Elisabeth, Gräfin of Hanau-Münzenberg, mother of Landgrave Wilhelm VI

In 1866, the end came. Elector Friedrich-Wilhelm of Hesse, full of grievances against Prussia, threw in his lot with Austria when Prussia was at war with Austria. The electorate was at once overrun with Prussian troops; Cassel was occupied (20 June); and the Elector was taken as a prisoner to Stettin. By the Peace of Prague, Electoral Hesse was annexed to Prussia.


Landgrave Wilhelm VI was born in Cassel, the son of Wilhelm V (whom he succeeded) and his wife Amalie-Elisabeth, Gräfin of Hanau-Münzenberg (daughter of Philipp-Ludwig II of Hanau-Münzenberg and his wife Countess Catharina Belgica of Nassau). His mother remained his guardian until he came of age. Despite Hesse-Cassel’s defeat in the Thirty Years’ War, Wilhelm’s mother did not wish to acknowledge the accord of 1627.

This required that the unmarried Marburger heir and the Landgraves of Hessen-Darmstadt should fall, but Amalie-Elisabeth had other ideas and led Hesse-Cassel in 1645 into the “Hessenkrieg”, ruling as Landgräfin on her son’s behalf. This war began when Hesse-Cassel troops began to besiege the city of Marburg. Three years later, in 1648, the war ended with a victory for Cassel, although the citizens of Darmstadt also gained from it.

Domination over the Marburger territories went over to the landgrave of Hesse-Cassel, after the accord was dissolved and a new agreement was reached. Wilhelm VI succeeded in what his ancestors had tried to do in vain since 1604, that is, to end the Hesse-Marburg landgraviate, and to annex the Marburger lands to Hesse-Cassel.

After these wars, Wilhelm VI attended above all to the extension of the universities within his domains and the foundation of more new Lehranstalts. To finally resolve the quarrel with Landgrave Georg II of Hesse-Darmstadt, Wilhelm VI delivered to Georg II the territory around Gießen, along with Ämtern by Biedenkopf.

Shortly before his death, Wilhelm VI joined the League of the Rhine on its foundation in 1658. He also sought to effect a union between his Lutheran and Reformed subjects, or at least to lessen their mutual hatred. In 1661 he had a colloquy held in Kassel between the Lutheran theologians of the University of Rinteln and the Reformed theologians of the University of Marburg.

Wilhelm VI died at Haina in 1663. Control of his Landgraviate went to his eldest son Wilhelm VII, though – not yet of age – he remained under the guardianship of his mother Hedwig Sophie of Brandenburg until his early death in 1670.

Marriage and issue

Landgrave Wilhelm VI married Margravine Hedwig-Sophie of Brandenburg (1623–1683), daughter of daughter of Georg-Wilhelm, Elector of Brandenburg and Elizabeth-Charlotte of the Palantine of the Rhine. Their children were:

Margravine Hedwig-Sophie of Brandenburg

* Charlotte Amalie (1650–1714), married Christian V of Denmark
* Wilhelm VII (1651–1670), his successor, Landgraf 1663-1670.
* Luise (1652-1652)
* Charles (1654-1730), Landgraf 1670-1730
* Philipp (1655-1721), Landgrave of Hesse-Philippsthal, married Katharina-Amalia Gräfin von Solms-Laubach
* Georg of Hesse-Kassel (1658–1675);
* Elisabeth-Henriëtte (8 November 1661-1683), married King Friedrich I of Prussia as his first wife.

Friedrich V, Elector Palantine of the Rhine

Princess Elizabeth (Stuart) of England, Scotland and Ireland

Wilhelm VI’s mother-in-law, Elizabeth Charlotte of the Palantine of the Rhine was the daughter of Friedrich IV, Elector Palatine of the Rhine, and Louise-Juliana of Orange-Nassau. Her brother Friedrich became famous as the Elector-Palatine Friedrich V and “Winter King” of Bohemia. Friedrich’s daughter Sophia (1630–1714), with his wife, Princess Elizabeth (Stuart) of England, Scotland and Ireland, was the heir presumptive to the thrones of England and Ireland by the Act of Settlement, 1701. Sophia, married Ernst-August, Elector of Hanover. Her son became King George I of Great Britain in 1714.

Sophia of the Palatine of the Rhine

King George I of Great Britain was the grandfather of my previous blog entry, Prince August-Ferdinand of Prussia, making Landgrave Wilhelm VI and his wife, Margravine Hedwig-Sophie of Brandenburg the great-great grand uncle and aunt to both Friedrich II the Great of Prussia and his youngest brother, Prince August-Ferdinand of Prussia.