Landgraviate of Hesse-Kassel

The Landgraviate of Hesse-Kassel (Landgrafschaft Hessen-Kassel), known as Hesse-Cassel during its existence, was a state in the Holy Roman Empire under directly subject to the Emperor that came into existence when the Landgraviate of Hesse was divided in 1567 upon the death of Philip I, Landgrave of Hesse.

His eldest son William IV inherited the northern half and the capital of Kassel. The other sons received the Landgraviate of Hesse-Marburg, the Landgraviate of Hesse-Rheinfels and the Landgraviate of Hesse-Darmstadt.

The Landgrave of Hesse-Kassel was elevated to the Electorate of Hesse and Landgrave William IX was elevated to Imperial Elector during the reorganization of the Empire in 1803, in the midst of the Napoleonic wars, and later occupied by French troops and became part of the Kingdom of Westphalia, which was a French satellite state.

History
The line of Landgraves was founded by William IV, surnamed the Wise, the eldest son of Philip I. On his father's death in 1567, he received one half of the Landgraviate of Hesse, with Kassel as his capital; and this formed the Landgraviate. In 1604, additions were made when Maurice inherited the Landgraviate of Hesse-Marburg from his childless uncle, Louis IV.

In 1605, William IV turned Protestant, became involved later in the Thirty Years' War, and, after being forced to cede some of his territories to the Landgraviate of Hesse-Darmstadt, abdicated in favour of his son William V. His younger sons received apanages, which created several cadet lines of the house. The family line of the Landgraviate of Hesse-Rotenburg survived till 1834. On the death of William V, whose territories had been conquered by the Imperial Army of the Holy Roman Empire, his widow Landgravine Elisabeth Amalie of Hesse-Darmstadt, as regent for her son William VI, reconquered the state. With the aid of the French and Swedes, she held it, together with part of Westphalia.

At the Peace of Westphalia, accordingly, Hesse-Kassel was augmented by the larger part of the County of Schaumburg and by the Hersfeld Abbey, secularized as a principality of the Empire. The Landgravine Elisabeth Amalie of Hesse-Darmstadt introduced the rule of primogeniture. William VI, who came of age in 1650, was an enlightened patron of learning and the arts. He was succeeded by his son William VII, Landgrave of Hesse-Kassel, then an infant, who died in 1670. He was succeeded by his brother Charles I.

Charles' chief claim to notability is that he was the first ruler to adopt the system of hiring his soldiers out to foreign powers as mercenaries, as a means of improving the finances of his principality. Frederick I of Sweden, the next landgrave, had become by marriage King of Sweden. On his death, he was succeeded in the landgraviate by his brother William VIII, who fought as an ally of Kingdom of Great Britain during the Seven Years' War.

His successor, Frederick II, who had become a Catholic, leased 22,000 Hessian troops to his nephew George III of Great Britain for about £3,191,000; George used the troops in the war against the rebellion of the Thirteen Colonies. This action, often bitterly criticized, has of late years found apologists. Historians argue that the troops were Auxiliaries or mercenaries, and that the practice was quite common. Frederick II used the revenues derived from the hire for the development of the economic and intellectual life of the country. Due to their involvement in the American War of Independence, "Hessian" has become an American slang term for all German soldiers deployed by the British in the war. One such regiment was the Musketeer Regiment Prinz Carl.

Since the early years of the Reformation, the House of Hesse was Protestant, with only a few exceptions. Landgraves Philip I, William V, and Maurice married descendants of King George of Bohemia. From William VI onwards, mothers of the heads of Hesse-Kassel were always descended from William the Silent, the leader of the Dutch to independence on basis of Calvinism.

The Landgraviate of Hesse-Kassel expanded in 1604 when Maurice, Landgrave of Hesse-Kassel inherited the Landgraviate of Hesse-Marburg from his childless uncle, Louis IV, Landgrave of Hesse-Marburg (1537–1604).

During the Thirty Years' War, the Calvinist Hesse-Kassel proved to be Sweden's most loyal German ally. Landgrave William V and, after his death in 1637, his widow Amelia of Hanau, a granddaughter of William the Silent, as regent supported the Protestant cause, and the French and Swedes throughout the war. They maintained an army, garrisoning many strongholds, including Dorsten, the strongest fortress on the right bank of the Rhine which was subsequently lost as the Siege of Dorsten. Meanwhile, Hesse-Kassel was occupied by Imperial troops.

William V was succeeded by Landgraves William VI and William VII. Under King Frederick I of Sweden, Hesse-Kassel was in personal union with Sweden from 1730–51. But the King's younger brother, Prince William, ruled in Kassel as regent until he succeeded his brother, reigning as William VIII until 1760.

Although it was a fairly widespread practice at the time to rent out troops to other princes, it was the Landgraves of Hesse-Kassel who were notable for hiring out contingents of their army as mercenaries during the 17th and 18th centuries. Hesse-Kassel maintained 7% of its entire population under arms throughout the eighteenth century. This force served as a source of mercenaries for other European states.

During the 17th century, the landgraviate was internally divided for dynastic purposes, without allodial rights, into:
 * the Landgraviate of Hesse-Rotenburg (1627–1834)
 * the Landgraviate of Hesse-Wanfried-(Rheinfels) (1649–1755)
 * the Landgraviate of Hesse-Philippsthal
 * Landgraviate of Hesse-Philippsthal-Barchfeld

These were reunited with the Landgraviate of Hesse-Kassel when each particular branch died out without issue.

Aftermath
Following the reorganization of the German states during the German mediatisation of 1803, the Landgraviate of Hesse-Kassel was raised to the Electorate of Hesse and Landgrave William IX was elevated to Imperial Elector, taking the title William I, Elector of Hesse. The principality thus became known as Kurhessen, although still usually referred to as Hesse-Kassel.

In 1806, William I was dispossessed by Napoleon Bonaparte for his support of the Kingdom of Prussia. Kassel was designated as the capital of a new Kingdom of Westphalia, where Napoleon appointed his brother Jérôme Bonaparte as king. Following Napoleon's defeat in 1813, the elector was restored. Although the Holy Roman Empire was then defunct, William retained his title of Elector, as it gave him pre-eminence over his cousin, the Grand Duke of Hesse. From 1813 onwards, the Electorate of Hesse was an independent country and, after 1815, a member of the German Confederation.

William's grandson, Elector Frederick William, sided with the Austrian Empire in the Austro-Prussian War. After the Prussian victory, his lands were annexed by Prussia in 1866. Along with the annexed Duchy of Nassau and Free City of Frankfurt, Hesse-Kassel became part of the new Province of Hesse-Nassau of the Kingdom of Prussia.

In 1918, Prince Frederick Charles of Hesse, younger brother of the head of the house and a brother-in-law of Emperor William II, was elected by the pro-German Finnish government to be King of Finland, but he never reigned.

Later in 1918, Hesse-Nassau became part of the Free State of Prussia, which existed until 1944. From 1944–45 as part of Nazi Germany, it was divided into the Prussian provinces of Kurhessen and Nassau. From 1945–46, it was renamed Greater Hesse (Großhessen) and was part of the US occupation zone in Germany. From 1946 onwards, it was reorganised into the State of Hesse, a federal state of West Germany.

In 1968, the head of the House of Hesse-Kassel became the head of the entire House of Hesse due to the extinction of the House of Hesse-Darmstadt.

Other uses
The village of Hessen Cassel, Indiana near Fort Wayne, founded by German immigrants, is named for the Landgraviate of Hesse-Kassel. In 1776, a Hessian military leader, Wilhelm von Knyphausen, helped Great Britain in the American Revolution.