Question

which is the correct order of events that occurred after austria - hungary declared war on serbia?
russia mobilized its forces, prompting germany to declare a two - front war against russia and france.
france mobilized its forces, prompting germany to declare a two - front war against france and russia.
germany mobilized its forces, prompting russia and france to declare war against germany and austria - hungary.
austria - hungary mobilized its forces, prompting russia and germany to declare war against austria - hungary and france.

Explanation:

After Austria - Hungary declared war on Serbia, Russia mobilized its forces in support of Serbia. This mobilization by Russia led Germany to declare a two - front war against Russia and France. France mobilized later in response to the German threat. Germany's mobilization was part of its war plans and was not the first event after Austria - Hungary's declaration of war. Austria - Hungary had already declared war and its mobilization was not the trigger for the broader war in the order described in the options.

Answer:

Russia mobilized its forces, prompting Germany to declare a two - front war against Russia and France.