During the interval between the peace of Tilsit and the outbreak of the war with Austria in 1809, the Prince of Ponte Corvo returned to his duty of administering Hanover. Pursuing his former policy of ingratiating himself with everybody, he renewed his old friendships with all classes, and gained the goodwill of his neighbours in Denmark and Swedish Pomerania, showing a suavity which was in marked contrast to rigid disciplinarians of the school of Davout. Such conduct, however, did not gain the approval of the Emperor, whose policy was, by enforcing the continental system, to squeeze to death the Hanseatic towns, which were England's best customers.

The Marshal was so keenly aware of the displeasure of the Emperor and the hatred of many of his advisers, especially of Berthier, the chief of the staff, that he actually asked to be placed on half pay at the commencement of the campaign of 1809, but the Emperor refused his request. He had determined to end the unceasing struggle between himself and Bernadotte. The battle of Wagram gave him his opportunity. On the first day of the battle, the Marshal had severely criticised, in the hearing of some of his officers, the methods the Emperor had adopted for crossing the Danube and attacking the Archduke Charles, boasting that if he had been in command he would by a scientific manœuvre have compelled the Archduke to lay down his arms almost without a blow. Some enemy told the Emperor of this boast. On the next day Bernadotte's corps was broken by the Austrian cavalry and only saved from absolute annihilation by the personal exertion of the Marshal and his staff, who, by main force, stopped and re-formed the crowd of fugitives. The Emperor arrived on the scene at the moment the Marshal had just succeeded in staying the rout, and sarcastically inquired, "Is that the scientific manœuvre by which you were going to make the Archduke lay down his arms?" and before the Marshal could make reply continued, "I remove you, sir, from the command of the army corps which you handle so badly. Withdraw at once and leave the Grand Army within twenty-four hours; a bungler like you is no good to me." Such treatment was more than the Marshal's fiery temperament could stand, and accordingly, contrary to all military regulations and etiquette, he issued a bulletin without the authority of the Emperor praising the Saxon troops, and thus magnifying his own importance. The Emperor was furious, and sent a private memorandum to the rest of the Marshals declaring that, "independently of His Majesty having commanded his army in person, it is for him alone to award the degree of glory each has merited. His Majesty owes the success of his arms to the French troops and to no foreigners.... To Marshal Macdonald and his troops is due the success which the Prince of Ponte Corvo takes to himself." It seemed as if Bernadotte's career was finished.

The Emperor found he had no longer any reason to fear him, and for the moment determined to crush him completely. So when he heard that Clarke had despatched the Prince to organise the resistance to the English at Flushing, he at once superseded him by Bessières. But the prospect of an alliance by marriage with either Russia or Austria once again caused the Emperor to reflect on the necessity of avoiding scandal and discord in his own family; accordingly he determined to try and propitiate the Marshal by sending him as his envoy to Rome. To a born intriguer like Bernadotte, Rome seemed to spell absolute exile, and accordingly, in the lowest of spirits, he set about to find excuse to delay his journey, little thinking that fortune had turned and was at last about to raise him to those heights of which he had so long dreamed. Long before, in 1804, at the time of the establishment of the Empire, he had secretly visited the famous fortune-teller, Mademoiselle Lenormand, who had told him that he also should be a king and reign, but his kingdom would be across the sea. His boundless ambition, stimulated by Southern superstition, had fed itself on this prophecy, even when the breach with Napoleon seemed to close the door to all hope.

In May, 1809, a revolution in Sweden had deposed the incapable Gustavus IV. and set up as King his uncle Charles, Duke of Sudermania. The new King, Charles XIII., was old and childless. Accordingly the question of the succession filled all men's minds. With Russia pressing in on the east and Denmark hostile on the west, it was important to find some one round whom all might rally, by preference a soldier. It was of course obvious that France, the traditional ally of Sweden, dominated Europe. Accordingly the Swedes determined to seek their Crown Prince from the hands of Napoleon. Now, of all the Marshals, Bernadotte had had most to do with the Swedes. At Hamburg he had had constant questions to settle with the Pomeranians. At the time of Blücher's surrender at Lübeck he had treated with great courtesy certain Swedish prisoners. It seemed therefore to the Swedish King's advisers that the Prince of Ponte Corvo, the brother-in-law of King Joseph, the hero of Austerlitz, was the most suitable candidate they could find. Napoleon, however, was furious when he heard that a deputation had arrived to offer the position of Crown Prince of Sweden to Bernadotte. Too diplomatic to refuse to allow the offer to be made, he set to work at once secretly to undermine the Marshal's popularity in Sweden, and while pretending to leave the decision to Bernadotte himself, assured his friends that the Marshal would never dare to accept the responsibility. But Napoleon had miscalculated. Some kind friend informed the Marshal of what the Emperor had said, and, as Bernadotte himself admitted, it was the taunt, "He will never dare," which decided him to accept the Swedish offer. Before the Crown Prince elect quitted France the Emperor attempted to place on him the condition that he should never bear arms against him; but Bernadotte, foreseeing the future, refused to give any such promise, and at last the Emperor gave in with the angry words, "Go; our destinies will soon be accomplished!"

The Crown Prince took with him to Sweden his eldest son, who had curiously, by the whim of his godfather, Napoleon, been named Oscar. But his wife, Désiré, could not tear herself away from Paris, where she had collected a coterie of artists and writers; her salon was greatly frequented by restless intriguers like Talleyrand and Fouché. Woman of pleasure as she was, the gaiety of Paris was the breath of her nostrils. Accordingly the Crown Princess remained behind, as it were the hostage for the Prince's good behaviour, but in reality a spy and secret purveyor of news hostile to Napoleon.

On landing in Sweden the Crown Prince took all by storm. His good looks, his affability, his great prestige and his apparent love for his new country created an enthusiasm almost beyond belief. But while everything seemed so favourable the crafty Gascon from the first foresaw the dangers which beset his path. Napoleon hated him. Russia looked on him with distrust and desired to absorb Sweden. England and the other Powers mistrusted him as the tool of the Emperor. Accordingly, the moment he landed at Gothenburg the Prince clearly defined the line he intended to pursue, exclaiming, "I refuse to be either the prefect or the custom-house officer of Napoleon." This decision meant a complete reversal of Swedish foreign policy and a breach with France. Fortunately for Bernadotte the old King, Charles XIII., was only too glad to leave everything to his adopted son. Since it was impossible to make a complete volte face in a moment, the Crown Prince was content to allow the Swedes to taste to the full the misery of trying to enforce the continental system. For he knew what disastrous effect a war with England would have on Swedish trade, and he foresaw that his subjects would soon be glad to accept any policy whereby their sea-borne commerce might be saved. While the Swedes were learning the folly of fighting the mistress of the sea, the Crown Prince had time to make his plans, so that when the moment arrived he might step forward as the saviour of the country. It was quite clear that a breach with France must mean the loss of Pomerania and all hope of regaining the lost provinces on the southern shores of the Baltic. But Bernadotte determined to find in Norway a quid pro quo for Pomerania. To force Russia, the hereditary foe of Sweden, to make her hereditary ally, Denmark, grant Norway to Sweden, would be a master-stroke of diplomacy, while an alliance with Russia would guarantee the Swedish frontiers and would bring peace with England, because Russia was on the point of breaking with the continental system. The Swedes would thus gain Norway and recover their sea-borne trade, while the Crown Prince would be acknowledged as the legitimate heir of the royal house of Vasa and no longer regarded as an interloper, a mere puppet of Napoleon.

Success crowned the efforts of the elated Gascon. The Czar, with the prospect of a French invasion at his door, was delighted beyond measure to find in Sweden an ally instead of a foe. In August, 1812, he invited the Crown Prince to Russia and the treaty of Åbö was signed, whereby Russia promised to lend her aid to Sweden to gain Norway as the price of her help against France; a little later a treaty was concluded between England and Sweden. The Crown Prince returned from Åbö full of relief; not only was he now received into the inner circle of legitimate sovereigns, but the Czar had actually volunteered that if Napoleon fell "I would see with pleasure the destinies of France in your hands." Alexander had kindled a flame which never died as long as Bernadotte lived. The remainder of his life might be summed up as an effort to gain the crown of France, followed by a period of vain regrets at the failure of his hopes.

On returning to Stockholm the Crown Prince found himself surrounded by a crowd of cosmopolitan admirers, the most important of whom was Madame de Staël, who regarded him as the one man who could restore France to prosperity. His flatterers likened him to Henry IV. and harped on the fact that he also came from Béarn. But in France men cursed the traitorous Frenchman who was going to turn his sword against his country, and his name was expunged from the list of the Marshals and from the rolls of the Senate, while the Emperor bitterly regretted that he had not sent him to learn Swedish at Vincennes, the great military prison. When, in accordance with his treaty obligations, early in 1813 the Crown Prince of Sweden landed at Stralsund to take part in the war against Napoleon, his position was a difficult one. The one object of the Allies was to overthrow Napoleon, the one object of the Crown Prince was to become King of France on Napoleon's fall. The Allies therefore had to beat the French troops, but the Crown Prince would ruin his hopes if French soldiers were beaten by the troops under his command. It was clear that Napoleon could only be overcome by the closest co-operation of all the Allies. Accordingly the Czar and the King of Prussia summoned the Crown Prince to a conference at Trachenberg in Silesia and did their best to gratify his pride. The plan of campaign was then arranged, and the Prince returned to command the allied forces in Northern Germany. At St. Helena the Emperor declared that it was Bernadotte who showed the Allies how to win by avoiding all conflict with himself and defeating the Marshals in detail. With great bitterness he added, "He gave our enemies the key to our policy, the tactics of our armies, and showed them the way to the sacred soil of France." Be this as it may, his conduct during the campaign justified the suspicion with which he was regarded by friend and foe. Only three times did the Prince's army come in contact with the forces of the Emperor. At Grosbeeren and Dennewitz, where his divisional officers fought and won, the Prince kept discreetly in the rear. At Leipzig he held back so long that the French army very nearly escaped. It was the taunt of his chief of the staff, "Do you know that the soldiers say you are afraid and do not dare to advance?" which at last forced him into battle. But while thus he offended his allies, he gained no respect from his former countrymen. He had always believed that his presence alone was sufficient to bring over the French troops to his side, but his first attempt ought to have shattered this delusion. At Stettin, during the armistice, he entered the fortress and tried to seduce the governor, an ex-Jacobin and erstwhile friend. As he left the town a cannon was fired and a ball whistled past his ear. He at once sent a flag of truce to demand an explanation for this breach of the etiquette of war, whereon his friend the ex-Jacobin replied, "It was simply a police affair. We gave the signal that a deserter was escaping and the mainguard fired." In spite of this warning and many other indications, Bernadotte failed to understand how completely he had lost his influence in France, and while the Allies were advancing on Paris his secret agents were busy, especially in Southern France, trying to win the people to his cause. Keeping well in the rear of the invading armies, he entirely neglected his military duties and passed his time listening to the reports of worthless spies. The result of his intrigues was that he quite lost touch with the trend of events at the front, and when Paris fell, instead of being on the spot, he was far away. The Czar, long disgusted with his delays, no longer pressed his suit, and finding an apparent desire for a Bourbon restoration, accepted the return of that house. So when the Crown Prince came to Paris he found nothing for it but to make his best bow to the Bourbons and slink away home to gain what comfort he could in the conquest of Norway. Thus once again was Sièyes' saying proved correct: "He is a blackbird who thinks himself an eagle."

On his return home his Swedish subjects gave their Crown Prince a very warm welcome. They knew of none of his intrigues or tergiversations, they only saw in him the victorious conqueror of Napoleon, who, by his successful campaigns, was bringing peace and prosperity to Sweden, by his diplomacy had acquired Norway, and by his clever huckstering had gained twenty million francs for ceding to France the isle of Guadaloupe, of which Sweden had never taken possession, and another twelve millions for parting with the lost Pomeranian provinces. But in spite of his popularity at home the Crown Prince had much to make him anxious abroad. At the Congress of Vienna a strong party backed the claims of the deposed Gustavus IV., and it was only the generous aid of the Czar which defeated this conspiracy. Further, the attitude of the Powers clearly showed him how precarious was the position of an intruder among the hereditary rulers of Europe. Consequently, when Napoleon returned from Elba the Prince exclaimed: "The cause of the Bourbons is for ever lost," and for a moment thought of throwing in his lot with the Emperor. But the sudden defeat of Murat came as a warning, and he hastened to offer the aid of twenty-six thousand troops to the Allies. Though outwardly in accord with them, the Crown Prince secretly hoped for the victory of Napoleon; to his intimates he proclaimed that "Napoleon was the first captain of all ages, the greatest human being who had ever lived, superior to Hannibal, to Cæsar, and even to Moses." Whereat the Crown Princess, who had at last rejoined her husband in Sweden, replied: "You ought to exclude Moses, who was the envoy of God, whereas Napoleon is the envoy of the Devil."

The news of Waterloo once again drove the Prince's ideas into their old current. Surely France must now recognise that he alone could save her; but the second restoration dashed his hopes to the ground. Yet hope springs eternal in the human breast, and Bernadotte, year by year, watched the trend of French politics with an anxious eye. Even as late as the Revolution of 1830 he still thought it was possible that France might call him to be her ruler, and he never lost the chance of doing the Bourbons an ill-turn. In spite of these intrigues, save for an appeal lodged in 1818 against the high-handed conduct of the Quadruple Alliance in interfering between Sweden and Denmark, Bernadotte's European career really ended with the fall of Napoleon. As Charles XIV. he ascended the Swedish throne on February 18, 1818, on the death of his adoptive father. As King he pursued the same policy as Crown Prince, alliance with Russia. His internal policy was based on the principle of maintaining his dynasty at all costs. With this object, in Sweden he ruled more or less as a benevolent despot, consulting his States General as little as possible, paying the greatest attention to commerce and industry, and opening up the mines and waterways of the country. In Norway, however, where the Storthing had long enjoyed great powers, he ruled as a liberal constitutional monarch, and with such good fortune did he and his successors pursue their policy that of all the diplomatic expedients arranged at the Congress of Vienna, the cession of Norway to Sweden stood the test of time the longest, and it was not till 1906 that the principle of nationality was at last enforced in Scandinavia.