The correct answer to this open question is the following.
The decisions made by the Congress of Vienna were able to prevent war although, in reality, different conditions and situations presented that made the decisions made in the Congress of Vienna difficult to follow up and prevent war in Europe.
The Congress of Viena was held to provide peace in western Europe after all the consequences of the Napoleonic Wars and the French wars.
One of the goals of the Congress of Vienna (1814-1815) was to restore Europe to the way it was before the French Revolution and Napoleonic Wars.
When Napoleon was defeated, the victorious countries met to establish a plan that could offer a relative past to Europe after so many years of conflict. So they met in Vienna, Austria in the so-called Congress of Vienna, to change things after the reorder of the Napoleonic wars, trying to reestablish some monarchies. Peace and understanding functioned relatively well until the previous years of World War 1.
Austria was the host of the Congress of Vienna, held from November 1814 to June 1815. During this time, European ambassadors met to discuss the plans for peace in Europe after so much damage and destruction due to the French Revolution and later, to the Napoleonic Wars. The delegates reached agreements about the reorganization of territories in Europe and the balance of power in the region.
