The immediate occasion of the conference was the necessity of settling the status of the Grand Duchy of Luxemburg, which, after the downfall of Napoleon, had been added to the dominions of the King of the Netherlands as a separate and independent state and made a member of the German Confederation.
Notwithstanding the dissolution of the Confederation, Luxembourg continued to be occupied by Prussian troops, the French government insisting upon the removal of these troops and threatening war to enforce the demand, resulting in the Luxembourg Crisis.
The conference was called to avert the new danger to the peace of Europe, and it solved the problem by the statesmanlike device of placing the grand duchy under the collective guarantee of the Great Powers as a permanently neutralized territory.
The distinction between individual and collective guarantee resulted in some confusion when the Germans invaded both Belgium and Luxembourg in August 1914.
However, since Belgium was individually guaranteed by the major powers (including Britain), the British government felt obliged to defend its neutrality against German invasion.