(A) They were appalled at how Serbia had responded to a declaration of war
(B) ** They belonged to alliances that obligated them to take action
(C) They wanted to bring a swift end to the battle before it went worldwide
(D) They knew that Austria-Hungary would never have a chance without their support
EXPLANATIONS BELOW
Concept note-1: -The immediate reason for Austria’s ultimatum was the assassination of Archduke Franz Ferdinand and his wife Sophie in Sarajevo, Bosnia on June 28, 1914 by the Bosnian Serb nationalist, Gavrilo Princip.
Concept note-2: -Threatened by Serbian ambition in the tumultuous Balkans region of Europe, Austria-Hungary determined that the proper response to the assassinations was to prepare for a possible military invasion of Serbia.
Concept note-3: -Russia. Following the declaration of war on Germany, Russian Emperor Nicolas II issued a manifesto announcing that in response to the Austro-Hungarian declaration of war against the Russian Empire, Russia would enter into war against Austria-Hungary. This occurred on on July 26, 1914.
Concept note-4: -The assassination of Austrian Archduke Franz Ferdinand (June 28, 1914) was the main catalyst for the start of the Great War (World War I). After the assassination, the following series of events took place: July 28-Austria declared war on Serbia.