John Ernst, Count of Nassau-Weilburg

John Ernst of Nassau-Weilburg (Weilburg, 13 June 1664 – Heidelberg, 27 February 1719) was an Imperial Generalfeldmarschall, from 1675 to 1688 Count and from 1688 till his death Prince (Fürst) of Nassau-Weilburg.

Biography
John Ernst was the eldest son of Frederick, Count of Nassau-Weilburg (1640–1675) and Christiane Elisabeth of Sayn-Wittgenstein (1646–1678). After the death of his parents, his regents were John, Count of Nassau-Idstein and after his death, John Louis, Count of Nassau-Ottweiler. In Juli 1679 John Ernst started his studies at the University of Tübingen. Between 1681 and 1682 he stayed at the court of King Louis XIV of France in the Palace of Versailles.

John Ernst became the only ruler of Nassau-Weilburg when his brother Frederick William Louis was killed in 1684 during the siege of Buda. His territories on the left bank of the Rhine were occupied by France and only returned after the Treaty of Ryswick in 1697.

John Ernst had an important military career. In 1684 he commanded a Dragoon regiment in the service of the Landgraviate of Hesse-Kassel. In 1688, at the start of the Nine Years' War, he defended Koblenz. Later he participated in the Siege of Mainz (1689), the Battle of Fleurus (1690) and the Battle of Landen (1693).

In September 1696 John Ernst entered as general in the service of the Electoral Palatinate as General, which enraged his former employer Charles I, Landgrave of Hesse-Kassel. After the Peace of Ryswick, John Ernst became governor of the Palatinate city of Düsseldorf.

In 1701, at the outbreak of the War of Spanish Succession, John Ernst raised an army, participated in the successful Siege of Landau in 1702 and the consequent chasing of an army under Marshal of France Tallard from the Hunsrück. For this achievement, he was made an Imperial Generalfeldmarschall.

When Prince Eugene of Savoy marched in 1703 to Bavaria against the French Marshal Villars, John Ernst stayed on the Rhine to defend Landau against Tallard. This led on November 15, 1703 to the Battle of Speyerbach. It was a terrible defeat. 8000 men were lost and John Ernst's eldest son, Colonel Frederick Ludwig of Nassau-Weilburg was killed. Hereafter, John Ernst never fought a major engagement again and withdrew from active service all together in 1706. He was Großhofmeister of the Elector Palatinate until 1716 and returned to Weilburg, where he died in 1719.

Marriage and issue
John Ernst married on April 3, 1683 Maria Polyxena of Leiningen-Dagsburg-Hartenburg (February 7, 1662 - April 22, 1725). They had 9 children :
 * Frederick Louis (1683–1703), killed in the Battle of Speyerbach
 * Charles August (1685–1753) married Princess Auguste Friederike Wilhelmine of Nassau-Idstein
 * Maria Polyxena (1686–1687)
 * Johanna Louise (1687–1688)
 * Charles Ernst (1689–1709)
 * Henry Louis (1690–1691)
 * Magdalena Henrietta (1691–1725) married Frederick William, 1st Prince of Solms-Braunfels
 * Albertina (1693–1748)
 * a daughter (1694)