- "Gads! I've got a beautiful sword! Crafted in Spain! But a man can't marry his sword, you know. I need a woman to sooth my brow! And here Bonaparte has already found a fiancée! Damn, he's a lucky dog. I wonder if he'll amount to anything?"
- ―Bernadotte to Arno Dorian, 1795.[src]
Formerly a high-ranking officer in the French Army, Bernadotte fought alongside Napoleon Bonaparte in the French Revolutionary Wars and subsequently the Napoleonic Wars before being appointed as heir to the Swedish and Norwegian throne
Bernadotte spent his youth as a stable boy and was nicknamed "Fanfan Belle-Jambe" for his muscular legs. At the age of 17, he joined the army as a private and continued to rise up the ranks after the French Revolution broke out.
- Bernadotte: "Gads! What a woman of passion! Désirée! My love for you burns as bright as your love letters to Bonaparte! Could you ever-?"
- Désirée: "Oh, Jean!"
- ―Bernadotte proposing to Désirée, 1795.[src]
By 1795, Bernadotte was a captain, alongside his fellow officer, Napoleon Bonaparte, the latter frequently having him do favors. Bernadotte himself felt lonely and desired a wife. When Napoleon's fiancée, Désirée Clary, was kidnapped by sans-culottes, he had Bernadotte and the Assassin Arno Dorian rescue her. As Désirée herself fought the sans-culottes alongside them, she and Bernadotte immediately became smitten with one another, although they both know that they could not be together.
As Napoleon later went to dine with Désirée at a restaurant, Bernadotte resolved to go there and bring her a silver pendant as a declaration of love. With Napoleon already suspicious, he sent Arno to investigate the matter. Arno learned of Bernadotte's plans, discovered several suspicious objects: Like a letter written by Napoleon and a silver pendant as a gift. He prepared to escort him out of the restaurant. However, the other patrons at the restaurant gossiped about Désirée, causing Bernadotte to attack them. In the ensuing fight, Arno was forced to protect him. Embarassed, Désirée told Bernadotte that she never wanted to see him again, leaving the latter heartbroken.
He began soliciting prostitutes and drinking heavily, which caused Désirée to regret her words, as she still loved him. She thus had Arno find Bernadotte and escort him back to her. To prove her love, she then sent Arno to recover her love letters to Napoleon, promising to burn them. Napoleon himself had shifted his attentions towards Joséphine de Beauharnais. As Arno returned with the letters, she burned them in front of Bernadotte, who proposed to her. At that moment, the three were attacked by thugs, whom they fought off. Afterwards, Désirée accepted Bernadotte's hand in marriage.
In the meantime, Bernadotte became a brigadier general, and, six months after that, a general of division. He continued to serve under Napoleon, including at his great victory at the Battle of Austerlitz. Bernadotte would eventually abandon his former revolutionary principles, when in 1810, the ailing Charles XIII of Sweden adopted him as his heir and crown prince. When the former died, Bernadotte was crowned King Charles XIV John of Sweden and Norway, and Désirée became his queen.