How did a local conflict in the Austrian-Hungarian Empire grow to a conflict between all of Europe?

Explanation:

In the times following the Austrian collapse in connections with Serbia, the rest of Europe, including Russia’s associates, Britain and France, seemed on with alarm, apprehending the expected disruption of a Balkans dispute that, if penetrated into by Russia, frightened to split into a general European war. The British Foreign Office requested its equivalents in Berlin, Paris, and Rome with the plan of a global organization directed at reducing the dispute; the German administration, though, was set against this idea and suggested Vienna go forward with its ideas.

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the congress realized that action had to be.