Why did the Congress of Vienna unite Belgium and the Netherlands in 1815?

Following the defeat of Napoleon, the Congress of Vienna (1815) united Belgium and the Netherlands primarily to create a stronger buffer state against potential future French expansion.12

The Allied powers, heavily influenced by Great Britain, were determined to prevent the Belgian territories from remaining under French control. By merging these territories with the former United Provinces, the powers sought to establish a more effective barrier than had existed previously.1

This political decision was made for the convenience of Europe and was implemented regardless of the wishes of the Belgian and Dutch populations. The resulting Kingdom of the Netherlands faced immediate challenges, as the two regions had developed distinct cultural, religious, and economic identities over the preceding centuries, eventually leading to the Belgian Revolution in 1830.13