Von Fersen's father, the de facto parliamentary leader of the Hats party, was the most politically influential man in Sweden at that time and also one of the richest in the realm.

On 3 July 1770, von Fersen made his first journey abroad with the intention of seeing the world and finishing his studies at military academies, including Brunswick, Turin, Strasbourg and Lüneburg.

[2] Von Fersen continued the Grand Tour by travelling to England where he stayed for roughly four months and met King George III and Queen Charlotte.

In the late summer of 1778, von Fersen traveled to Normandy with his friend, the Baron de Stedingk, to see a large army camp that was training under the command of the Duke of Broglie.

[citation needed] In December 1782, the French made sail for the West Indies and Venezuela, but word reached them of the signing of peace and the ships headed back to France.

Von Fersen was awarded the Order of Cincinnatus by Washington, though he was forbidden by his monarch to wear a medallion earned fighting in a republican war.

Gustavus promoted von Fersen to titulary-colonel in the Swedish army, chevalier of the Order of the Sword, and lieutenant-colonel of the light-horse cavalry of the King.

Gustavus also used his influence to persuade Louis to have von Fersen appointed proprietary colonel of the Royal Suédois French Army infantry regiment.

In August 1786, Vicomte de Calonne finally apprised Louis XVI of the desperate state of the French finances, and by the very end of the year it was announced that there would be a convening of an Assembly of Notables to discuss future measures.

It is a mania, everybody is an administrator and can talk only of progress; the lackeys in the antechambers are occupied in reading the pamphlets that come out, ten or twelve in a day, and I do not know how the printing-presses can do the work.

By the end of June, the monarchy had reinforced its concentration of regiments around the capital, ostensibly to maintain order in and around Paris, although many believed the troops would be turned against the recalcitrant Third Estate.

[10] Months later, with the revolution spreading to the rest of the country and the royal army in disintegration, the Flanders Regiment was brought to Versailles to replace the French Guards who had mutinied.

Von Fersen wrote: I can see clearly that they are dragging things along purposely to prevent the King of Sweden from sending troops this year; they fear his activity, and also that he may command in person.

On 20 June, the Tuileries was stormed by a large crowd and Louis was made to wear a red bonnet of liberty and drink a toast to the health of the people of Paris and the Nation.

Von Fersen heard the news while in Cologne: "Received last night at 10:30, from the Archbishop of Tours, the sad details of the death of the King of France".

[16] On 1 February, France officially declared war against Great Britain and the Dutch Republic, but the tide quickly turned against the French in the Netherlands.

He recognised Simolin [Russian ambassador to France]; I named myself; he made me a compliment, saying he ought to have known me by my handsome face ... On the whole, I found him a true Frenchman, vain, confident, heedless; with much intelligence and little judgement.

On 11 August he wrote: Having talked with La Marck on the means of saving the queen, and agreeing that there were none except to push forward at once a strong body of cavalry to Paris - which would be the easier to do at this moment, because there are no troops before the city and the granaries are full, - I went to see Mercy about it and found him all ice to the idea ...

Von Fersen and his best friend, Baron Taube, became two of the most influential advisers to the young king, inculcating in him a "steadfast opposition to Revolutionary France, close relations with Russia, and hostility to Denmark, with the ultimate objective of acquiring Norway".

"[22] In April, an attempt to trick the Uppsala orchestra into performing a composition containing an excerpt from the "Marseillaise" led to the trial and punishment of four known university radicals, one of whom was dismissed.

[citation needed] With the government nearly bankrupt, and poor harvests and declining trade undermining his efforts to resolve the issue without recourse to parliament, Gustav IV Adolf reluctantly announced the first assembly of the Riksdag.

Von Fersen, now Earl Marshal of Sweden, led a political faction ("the Gustavians") which supported Gustavus' son against the popular Crown Prince Charles August.

Rumours were rife throughout the country that he had been poisoned by the partisans of Gustav IV Adolf; von Fersen and his sister Sophie were seen as prime suspects.

General Silfversparre (sv), commander of the Stockholm garrison, was alerted to the possibility of disturbances but may himself have been a member of the court party that opposed von Fersen.

[24] The procession proceeded slowly through the Hornsgatan and Södermalm Square, and was met with threats and insults directed at von Fersen as soon as it entered the city.

Von Fersen's contemporary, Baron Gustaf Armfelt, stated afterward: One is almost tempted to say that the government wanted to give the people a victim to play with, just as when one throws something to an irritated wild beast to distract its attention.

[26] A few months after the murder, von Fersen and his family were cleared of any suspicion connected with the death of Carl August of Augustenburg, and he finally received a state burial with all pomp and ceremony.

In Beaumont's account, von Fersen left for the war in America in the early part of 1780 to avoid causing a scandal, as it was widely known that the two were close, and it was rumoured that he was the queen's lover.

Beaumont wrote in his memoirs that von Fersen asked Swedish minister to France Gustaf Philip Creutz to use his influence to get him appointed as aide-de-camp to Rochambeau.

[29] Starting in 2016, scientists at France's Research Centre for the Conservation of Collections (CRCC) uncovered some of the redacted text of the queen's letters to Fersen.