The conference of the six Great Powers which met at London in May, 1867, to settle the political order of northern Europe after the disruption of the German Confederation in 1866 is known as the London Conference of 1867. It resulted in the Treaty of London of May 11, 1867. The immediate occasion of the conference was the necessity of settling the status of the Grand Duchy of Luxemburg, which, after the downfall of the First 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, Luxemburg continued to be occupied by Prussian troops, the French government insisting upon the removal of these troops and threatening war to enforce the demand. 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 conference is notable for its clear recognition of the principle of neutralization and of the rights of a neutralized state, as well as the obligations incurred by the Powers joining in the collective guarantee. In an individual guarantee, such as that guaranteeing the neutrality of Belgium, powers which signed the treaty would be bound to individually defend a nation's neutrality regardless of the actions of the other signatories. In a collective guarantee, such as this treaty with Luxemburg, the major signatories would act in concert or would not be required to act at all. The distinction between individual and collective guarantee resulted in some confusion when the Germans invaded both Belgium and Luxemburg in August 1914. Since Germany inherited Prussia's 1867 commitment to a collective guarantee, by invading Luxemburg it rendered impossible any joint action in defense of Luxemburg's neutrality. Britain was therefore not required to intervene to defend Luxemburg. However, since Belgium was individually guaranteed by the major powers, the British government felt obliged to defend its neutrality against German invasion.
