In 1811 the growing hostility of Russia required the attendance of the Prince of Eckmühl at the headquarters of his command. Napoleon knew well that nobody would be quicker to discern any secret movement hostile to his interests than the man who in 1808 had done so much to check the regeneration of Prussia by enforcing his orders, playing on the Prussian King's fears and exposing the cleverness of the proposals of the patriotic Stein. The Marshal reached his headquarters at Hamburg early in February, and soon found his hands full. It was no longer a question of so disposing the corps committed to his care that he might cripple the English, "who since the time of Cromwell have played the game of ruining our commerce," but of preparing a mixed force of French, Poles, and Saxons, amounting to one hundred and forty thousand, for the contingencies of a war with Russia, or for the absolute annihilation of Prussia. To no other of his Marshals did the Emperor entrust the command of one hundred and forty thousand troops, and consequently the old enmities and jealousies broke out with renewed force. It was whispered that the Marshal's income from his investments, pay, and perquisites was over two million francs a year; that nobody in the imperial family had anything like as much, and people said it was better to be a Davout than a Prince Royal. The Prince disregarded all the annoying scandal his wife sent him from Paris, and quietly busied himself with preparing transport and equipping magazines for the coming war, diversified by an occasional thundering declaration informing the King of Prussia that his secret schemes were well known to the French authorities. But the subterranean jealousies bore their fruit. Nobody had a good word to say for Davout, and there was nobody to take his part. Most disastrously for the Grand Army the misunderstanding which existed between Berthier and Davout prevented their co-operation; and thus during the Russian campaign the rash empty-headed Murat had greater weight with Napoleon than Davout, the cautious yet tenacious old fighter. Accordingly at the battle of Moskowa, when Napoleon had his last chance of annihilating the Russians, he refused to listen to the Marshal, who pleaded to be allowed to turn the Russian left during the night. "No," said the Emperor, "it is too big a movement; it will take me too much off my objective and make me lose time." Davout, sure of the wisdom of this advice, once again renewed his arguments, but the Emperor rudely interrupted him with "You are always for turning the enemy; it is too dangerous a movement." So the battle of Moskowa was a disastrous victory, opening as it did the gates of Moscow without the annihilation of the Russian armed forces in the field. But it was greatly due to the Marshal that it was a victory at all, for the Russians fought with the greatest stubbornness; nearly all the French generals were wounded or killed, and at one moment a panic seized the troops. Then it was that the Prince of Eckmühl himself rallied the broken battalions and led them to the charge. In spite of a wound in the pit of his stomach, with bare head and uniform encrusted with mud and blood, he forced his weary soldiers against the foe and, as at Auerstädt, by sheer indomitable courage, compelled his troops to beat the enemy. His corps bore its share in the horrors of the retreat from Moscow, forming for some time the rear guard.
When Napoleon deserted the relics of the Grand Army at Vilma the Marshal's difficulties naturally increased, for his enemy Murat was now in command, and, as he wrote to his wife earlier in the campaign, "I am worth ten times as much when the Emperor is present, for he alone can put order into this great complicated machine." But the King of Naples did not long retain his command: he had not Davout's confidence in Napoleon and was disgusted with the ill-success of the campaign and afraid of losing his crown. The Marshal, ever loyal to the Emperor, would listen to none of the Gascon's diatribes, and told him plainly, "You are only King by the grace of Napoleon and by the blood of brave Frenchmen. You can only remain King by Napoleon's aid, and by remaining united to France. It is black ingratitude which blinds you." So Murat went off to Italy to plan treason, and Davout returned to Germany to place his life and reputation at the Emperor's service.
It fell to the Marshal's lot in 1813 to hold Northern Germany as part of the plan of campaign whereby the advance of the Allies was to be checked. The Emperor had determined to make an example of the town of Hamburg, to teach other German cities the fate to be expected by those who deserted him. His orders were that all those who had taken any share in the desertion were to be arrested and their goods sequestrated, and that a contribution of fifty million francs was to be paid by the towns of Lübeck and Hamburg. The Marshal carried out his orders. Hamburg writhed impotent at his feet and the "heavy arm of justice fell on the canaille." Only in the case of the contribution did he make any deviation from the Emperor's wishes, as it was inexpedient to drive all the wealthy people out of the state. In pursuance of the Emperor's plans, by the winter of 1813 Davout had made Hamburg impregnable. He had laid in huge supplies, and built a bridge of wood two leagues long joining Haarburg and Hamburg. With a garrison of thirty thousand men, danger threatened from within rather than from without, for Napoleon's bitter punishment of Hamburg, ending as it did with the seizure of eight million marks from the funds of the city bank, had made the name of France stink in the nostrils of the inhabitants. The Marshal was determined to hold the town to the last. In December, when provisions began to fail, the poor were banished from the city; those who refused to go were threatened with fifty blows of the cane. "At the end of December people without distinction of sex or age were dragged from their beds and conveyed out of the town." During the siege the Russian commander, Bennigsen, attempted by means of spies and proclamations to raise a rebellion in the fortress, but Davout's grip was too firm to be shaken, and a few executions cooled the ardour of the spies. It was not till April 15th that the Marshal was informed by a flag of truce of the fall of the Empire; not certain of the truth of the news, he refused to give up his command. At last, on April 28th, official news arrived from Paris, and on the following day the fifteen thousand men who remained of the original garrison of thirty thousand swore allegiance to the Bourbons and mounted the white cockade.
On May 11th General Gerard arrived to relieve Davout of his command. On his arrival in France the Prince of Eckmühl found himself charged with having fired on the white flag after being informed of Napoleon's abdication, of appropriating the funds of the Bank of Hamburg, and of committing arbitrary acts which caused the French name to become odious. His reply was first that until he had received official information of the fall of the Empire it was his duty to take measures to prevent Hamburg being surprised; that the appropriation of the funds of the bank was the only means of finding money to hold Hamburg; that he was not responsible for the continental system, and as a soldier he had only obeyed commands; that as a matter of fact he had contrived to have the heavy contribution lightened, and lastly, that during the siege he had only had two spies shot and one French soldier executed for purloining hospital stores. But in spite of his defence and the prayers of his fellow Marshals Louis refused to allow Davout to take the oath of allegiance, and accordingly when, in 1815, Napoleon returned from Elba, the Prince of Eckmühl alone of all the Marshals could hasten to the Emperor without a stain on his honour.
Immediately on his return the Emperor made a great call on the faithfulness of his friend, and told him he had chosen him as Minister of War. The Marshal begged for service in the field, but the Emperor was firm; Davout alone had held to him and all others had the Bourbon taint. Still the Marshal refused, pleading his brusque manners and well-known harshness; but at last the Emperor appealed to his pity, pointing out that all Europe was against him, and asking him if he also was going to abandon his sovereign. Thereon the Marshal accepted the post. It was no light burden that he had undertaken, prince of martinets though he was, to regenerate an army scattered to the winds. Everything was lacking—men, horses, guns, transports, stores, and ammunition. Yet he worked wonders, and by the beginning of June the Emperor had a field army of one hundred and twenty thousand men, with another quarter of a million troops in formation in France. On the return of the Emperor to Paris after the disaster at Waterloo the Marshal in vain besought him to dissolve the assemblies and proclaim a dictatorship, but Napoleon's spirit was broken and the favourable moment passed by. Meanwhile, the Emperor remained in idleness at Malmaison, and by the 28th of June the Prussians arrived near Paris with the intention of capturing him; but the Prince of Eckmühl warded off the danger by barricading or burning the bridges across the Seine and manœuvring sixty thousand troops in front of Blücher. Thanks to this Napoleon escaped to Rochfort, and owed his safety to Davout, for Blücher had sworn to catch him, dead or alive.
On the evacuation of Paris the Marshal withdrew westwards with the remnant of the imperial army, now called the Army of the Loire. But as soon as Louis had once again ascended the throne he relieved Davout, making Gouvion St. Cyr Minister of War and Macdonald commander of the Army of the Loire. The Marshal spent some months in exile, but was allowed to return to France in 1816. However the mutual distrust between him and the Bourbons could not be overcome, and, although he took the oath of allegiance and received the cross of St. Louis, he never attempted to return to public life, and died of an attack of pleurisy on June 1, 1823.
The causes of the success of the Prince of Eckmühl are easy to ascertain: acute perception, doggedness of purpose, and a devotion which never faltered or failed, are gifts which are bound to bring success when added to an exceptional run of good fortune. Among the Marshals there were many, no doubt, who had as quick a perception and as vivid an imagination as Davout, but there was no one who had his massive doggedness and determination, and Bessières alone perhaps surpassed him in personal devotion to the Emperor. Much as we may see to blame in his untiring hounding down of the patriot Stein in Prussia, in his cruel exactions in Hamburg, and in the remorseless way he treated spies and deserters, we must remember that he did it all from motives of patriotism. Moreover, we cannot fail to admire a man who made it a principle, when he had received rigorous orders, to accept all the odium arising from their performance because he considered that, since the sovereign is permanent and the officials are changeable, it is important that officials should brave the temporary odium of measures which are but temporary. In his opinion the phrase, "If the King only knew," was a precious illusion which was one of the foundation-stones of all government: thus it was that in carrying out severe orders the Marshal never attempted to shield himself behind the name of the Emperor.
It was therefore from a spirit of patriotism, as the servant of the French Emperor, that Davout pressed relentlessly on those who tried to shake off the yoke of France. Stern as his nature was, he did not disguise from himself that his policy bore hardly on the conquered, for when Napoleon asked him, "How would you behave if I made you King of Poland?" he replied, "When a man has the honour to be a Frenchman, he must always be a Frenchman," but he added, "From the day on which I accepted the crown of Poland I would become entirely and solely a Pole, and I would act in complete contradiction to your Majesty if the interests of the people whose chief I was demanded that I should do so." As a soldier and an administrator, though he is rightly called the prince of martinets, yet nothing was more abhorrent to his eyes than red tape. Efficiency was everything, and efficiency he considered was only to be gained by personal inspection of detail considered in relation to existing conditions, and not by blind obedience to hard and fast rules. It was this habit of mind and readiness for all contingencies which won for him his titles of Duke of Auerstädt and Prince of Eckmühl, and made him the right-hand man of the great Emperor, who confessed that, "If I am always prepared, it is because before entering on an undertaking, I have meditated for long and foreseen what may occur. It is not genius which reveals to me suddenly and secretly what I should do in circumstances unforeseen by others: it is thought and meditation."