The rule of Napoleon restored peace to the Low Countries. The emperor carried the war far from the Belgian frontiers. The United Provinces had become a vassal kingdom, under the sceptre of Napoleon's brother Louis (1806), and, with the exception of a British landing on the island of Walcheren which miscarried (1809), the Belgian provinces were spared military operations up to the eve of the fall of the imperial régime.
In spite of the aversion caused by incessant conscription levies and by the strict censorship which stifled intellectual life, the Belgians benefited largely from the stern rule of the emperor, who re-established discipline and succeeded in substituting many Belgian notables for the French officials who had, up to then, governed the country. Prefects were placed at the head of the departments, which were divided into arrondissements and municipalities, each of these divisions possessing its own councils and its own courts: justices of the peace, courts of the first instance, courts of assize with a jury, above which were installed Courts of Appeal and a Court of Cassation. A "general code of simple laws," still known as the Code Napoleon, was substituted, in 1804, for the confused and intricate customs and laws preserved from the Middle Ages, and the fiscal methods were similarly transformed, inaugurating a system of direct and indirect taxes.
The Concordat, signed in 1801, re-established religious peace, Catholicism being recognized as the State religion. Churches were reopened and the observance of Sunday re-established.
Already, as First Consul, Napoleon devoted great attention to external trade. Ostend, which had been bombarded by the British in 1798, was restored, and after the peace of Amiens Antwerp enjoyed a few years of remarkable prosperity. In 1802, 969 ships entered the port; in 1803 the customs receipts rose to over 6,000,000 francs, in 1804 to over 8,000,000, and in 1805 to over 15,000,000. But the emperor's decree of November 21, 1806, establishing the Continental blockade, after the Battle of Trafalgar, converted Antwerp into a powerful naval base and a great centre of naval dockyards, without any benefit to the rest of the country. The activity of the nation was again confined to agriculture and industry. In this latter domain the period is marked by the introduction of spinning machinery by the Gantois Liévin Bauwens, who succeeded in obtaining models of the new British jennies. This was the origin of the prosperity of Ghent. While, in 1802, only 220 persons were employed in this industry, there were over 10,000 in 1810. Another innovation was brought about by a British engineer, William Cockerill, who, in 1799, initiated the use of new carding and spinning machines in Verviers. Many French cloth manufacturers were sent to the Walloon town by the French Government in order to study the new process.