The principality was proclaimed in 1813 when the victors of the Napoleonic Wars established a political reorganisation of Europe, which would eventually be defined by the Congress of Vienna.

This Triumvirate of 1813 formally took control over the liberated country on 20 November and declared the Principality of the United Netherlands a day thereafter.

While the Triumvirate offered to make him king, William Frederick turned it down, instead proclaiming himself "Sovereign Prince" of the United Netherlands on 2 December.

[7] The constitution, which would be in force for over a year, introduced a centralised monarchy in which the prince held much power, although it did contain some democratic elements.

The thirty most prominent families of Brussels expressed the wish to restore the old Governorate-general of the Austrians and this was provisionally instituted by the Allies in February 1814 as their military government.

For all intents and purposes, William Frederick had completed the House of Orange's three-century quest to unite the Low Countries.

William Frederick subsequently tried to get the assent of the (carefully selected) representatives of the Belgian people to the Dutch constitution, but encountered opposition from those who were suspicious of designs to undermine the position of the Catholic Church in those provinces.