End of the Napoleonic era. William Frederick, son of William V, is invited to return to the Netherlands. Two years later he becomes King William I of the Netherlands. The southern and northern Netherlands are unified to create a buffer against the expansionist tendencies of France.
At the 1815 Congress of Vienna, the victorious powers decided to create a buffer of strong states to contain the expansionist tendencies of France. The new Kingdom of the Netherlands, with William I as its king, was one of these. This unification of the southern and northern Netherlands was not universally welcomed. The south (present-day Belgium) was still primarily Catholic and continued to regard the northern Calvinists as heretics. It had particularly strong objections to the guarantees of equality offered by the new constitution of 1814 to all existing religious denominations. The bicameral parliament of the new state possessed few means of exercising influence on the government of the kingdom. As crown appointees, the members of the Upper House were popularly referred to as 'la ménagerie du roi'. The members of the Lower House were elected and included equal numbers of representatives from north and south. The parliament was initially docile but as time went on offered increasingly bitter resistance to matters such as the king's attempts to influence the curricula of the Catholic seminaries and the introduction of Dutch as the official language, even in the French-speaking provinces. Opposition was exacerbated by the decision to consolidate the debt burden of the two countries. This was seen as unreasonable because the debts of the north were much greater. The personality of William I did nothing to improve relations. He saw himself as an enlightened despot, an attitude which was accepted in the north but not in the south. He preferred to rule by Royal Decree, which did not require the approval of parliament. This made him even less popular.
King William I's services to the Netherlands were mainly economic. They earned him the nickname of 'the merchant king'. His attempts to weld the southern and northern Netherlands into a single state were motivated by commercial considerations. He recognised that the trading spirit of the north and the industrial activities of the south were complementary and that the apparently conflicting interests of the two regions could in fact work to the advantage of both. However, his hopes of forging a unified state out of the two countries were to be frustrated.
William invested heavily in new projects and expanded his own powers. He insisted that the Lower House should cede to him much of the right to decide on government finances and parliament had no say at all in the government of the colonies, which Britain had now returned to the Netherlands.
William instigated the establishment of a series of bodies designed to improve the national economy: in 1814, the Bank of the Netherlands, which was to start issuing Dutch bank notes; in 1818, a society (Algemene Maatschappij voor Volksvlijt) to encourage industry and combat the impoverishment of the country; and in 1824 the Netherlands Trading Society, founded to succeed the Dutch East India Company in the hope of winning back a major share of world trade. William also commissioned the construction of innumerable canals in both the north and the south and initiated the introduction of steam railways. His efforts to introduce modern industrial methods were chiefly successful in the south, but could not prevent the north remaining for a long time a country of poor farm labourers and artisans. The colonies - and in particular the Dutch East Indies (present-day Indonesia) - retained their economic importance. Although fewer than in the 17th and 18th centuries, they were still very extensive.