In becoming Jacques, first Emperor of Haiti, Dessalines did not lose sight of the necessity of making provision for the future good and tranquility. The French were still in possession of the Spanish portion of the island. On the 5th of January, 1805, General Ferrand, who was in command of this portion of the country, ordered a sudden attack upon the Haitians, among whom only those under 14 years of age were to be taken prisoners, the others being destined evidently to be massacred; the boys and the girls under 10 years were to be sold and kept on the plantations of the colony; whilst those between the ages of 12 and 14 years were to be sold and deported.

To avenge this barbarous decree, Dessalines, at the head of 25,000 soldiers, invaded the Spanish territory. He started on February 16, and on the 6th of March his army, victorious in every encounter, began to lay siege to Santo Domingo, which would undoubtedly have fallen before him had not a French squadron appeared with reinforcements on March 27. Fearing the possibility of French troops being landed on the coasts of Haiti during his absence, Dessalines was obliged to raise the siege and to evacuate the whole of the Spanish portion. His apprehensions were happily unfounded: the French had made no hostile demonstrations against Haiti. Nevertheless, Dessalines took all precautionary measures. He availed himself of the opportunity to organize his Empire. On the 20th of May, 1805, the first Haitian Constitution was proclaimed. Slavery was forever abolished. Dessalines, whose surroundings and early training had not been such as would tend to fit him to act the part of law-maker, proved to be an able one. He enacted a military penal code, laws concerning illegitimate children and divorce and a law establishing the courts and their jurisdiction. By decrees he settled the respective limits of the military divisions of the territory; he opened some ports to commerce with foreign countries; he regulated the coasting trade and established import and export taxes.

Notwithstanding all his excellent good qualities, he was a man with whom it was hard to agree. Above all, Dessalines was a man of action, and he owed his success to his untiring energy and to the use of force. Slave, soldier, or general, he accepted or enjoined discipline: he was accustomed to obey or to be obeyed. He was thus naturally led to consider as the best method of government that passive obedience which, as a military chief, he used to exact from his subordinates.
Death of Dessalines

This system succeeded in the struggle with the French; why then should it fail when applied to the administration? Of a hasty and petulant temper the new ruler of Haiti was as quick in forming a decision as in its execution; in consequence, he did not tolerate any discussion of his orders. Hence he ruled the State as he was wont to command his soldiers—as an absolute master. As a matter of fact, his rule was not far removed from the despotism of the French. The various Governors-General never had shown any respect for civil or political liberty. They relied upon the army and knew no restraint. To their minds the rights of the people were of no account. Having from his earliest years lived in such an atmosphere it was hardly possible to expect to find in Dessalines a liberal-minded ruler. And the purely rudimentary knowledge of his subordinates made them incapable of tempering the dictatorial power entrusted to him. A few of his economic and financial combinations were of necessity imperfect. In course of time these mistakes might have been remedied; and civil as well as political liberty would have prevailed. But Dessalines's contemporaries were very hasty men; his lieutenants took umbrage at the very tyranny they had contributed to create; and as the news spread that the most important amongst them were about to be arrested, they plotted a conspiracy. The discontent which some of the administrative measures had provoked among the people was taken full advantage of. The insurrection broke out on the 8th of October in the neighborhood of Port-Salut in the Southern Department. The insurgents acknowledged Henri Christophe, who was then Commander-in-Chief of the Army, as their leader. Pétion joined the revolt and caused the defection of the troops under his command. Port-au-Prince ceased accordingly to acknowledge Dessalines's authority. The Emperor, unaware of these events, had left Marchand, his capital, on October 15, en route for the South, where he was going to reestablish peace and order. On his way soldiers had been set by the conspirators; without the least suspicion of the trap set for him, he continued his way in full confidence, paying no heed to the warning which Colonel Leger, one of his aides-de-camp, gave him, as he was approaching Pont Rouge, at a short distance from Port-au-Prince, on the 17th of October, 1806. He did not realize the danger until he was completely surrounded on all sides. He tried to defend himself; but Garat, a young soldier, fired; Dessalines's horse fell to the ground. Charlotin Marcadieu, one of his aides-de-camp, hastened to his assistance. Just at that moment a volley of musketry was fired and Dessalines ceased to exist. Thus expired the liberator of Haiti, a victim of the sad customs of his time and of the very cause of liberty of which he had been the successful defender.

A woman from humble background, Défilée, took the mutilated body of the Emperor to bury him. Reviled by generations of Haitians, Dessalines gained a new and more prestigious profile as an icon of Haitian nationalism at the beginning of the 20th century.