The war-cloud arose on the political horizon in 1867, when Napoleon sought to purchase from the king of Holland the Duchy of Luxemburg, which was a personal fief of his kingdom, though it was inhabited by Germans, and which made him a member of the Germanic Confederation if he chose to join it.  In the time of Napoleon I. Luxemburg was defended by one of the strongest fortresses in Europe, garrisoned by Prussian troops; it was therefore a menace to France on her northeastern frontier.  As Napoleon III, promised a very big sum of money for this duchy, with a general protectorate of Holland in case of Prussian aggressions, the king of Holland was disposed to listen to the proposal of the French emperor; but when it was discovered that an alliance of the southern States had been made with the northern States of Germany, which made Prussia the mistress of Germany, the king of Holland became alarmed, and declined the French proposals.  The chagrin of the emperor and the wrath of the French nation became unbounded.  Again they had been foiled by the arch-diplomatist of Prussia.

All this was precisely what Bismarck wanted.  Confident of the power of Prussia, he did all he could to drive the French nation to frenzy.  He worked on a vainglorious, excitable, and proud people, at the height of their imperial power.  Napoleon was irresolute, although it appeared to him that war with Prussia was the only way to recover his prestige after the mistakes of the Mexican expedition.  But Mexico had absorbed the marrow of the French army, and the emperor was not quite ready for war.  He must find some pretence for abandoning his designs on Luxemburg, any attempt to seize which would be a plain casus belli.  Both parties were anxious to avoid the initiative of a war which might shake Europe to its centre.  Both parties pretended peace; but both desired war.

Napoleon, a man fertile in resources, in order to avoid immediate hostilities looked about for some way to avoid what he knew was premature; so he proposed submitting the case to arbitration, and the Powers applied themselves to extinguish the gathering flames.  The conference—­composed of representatives of England, France, Russia, Austria, Prussia, Holland, and Belgium—­met in London; and the result of it was that Prussia agreed to withdraw her garrison from Luxemburg and to dismantle the fortress, while the duchy was to continue to be a member of the German Zollverein, or Customs Union.  King William was willing to make this concession to the cause of humanity; and his minister, rather than go against the common sentiment of Europe, reluctantly conceded this point, which, after all, was not of paramount importance.  Thus was war prevented for a time, although everybody knew that it was inevitable, sooner or later.