Complicated conditions brought about world war i. which of the following was the single event that pushed europe off the brink into war? archduke ferdinand's assassination the sinking of the h. m.s lusitania the economic scramble for africa the invasion of france by austria

Archduke Ferdinand's Assassination
The assassination of Franz Ferdinand was the catalyst for war. The Austro-Hungarian authorities had for some time wanted to exert their influence over Serbia. The assassination provided an excuse to do just that. They had two options, first, a military strike which could cause problems as Russia had an agreement to defend Serbia in the event of an attack, or secondly, diplomatic pressure. On July 6th the German government stated that they would support Austria-Hungary's attempts to punish Serbia for the assassination. This is known as the "Blank Cheque". As a result of this support, the Austro-Hungarian government issued an ultimatum to Serbia on July 23rd, 1914. The ultimatum (which can be read in full here) asked the Serbs to hand over much of its sovereignty to the Austro-Hungarian government. It was not expected that the Serbs would agree to these demands and was in essence designed to provide a legitimate reason for taking military action: with the hope that this would result in other nations not becoming involved. Surprisingly the Serbs actually agreed to many of the demands with only a few minor points being disputed. This presented the Austrians with a problem. The Serbs had backed down, unexpectedly. Now the Russians made it clear that they would support Serbia if any action was taken and the French stated that they would support Russia if such action was necessary. On July 29th the Austrians declared war on Serbia. The Russians responded to this by mobilising their army the following day. This led to the German government demanding that the Russian mobilisation stopped, with the threat of German involvement in the conflict if this was ignored. At the same time the French were asked for assurances that they would remain neutral should Germany go to war with the Russian Empire. The French gave no such assurance and the Russians ignored the ultimatum. As a result, the Germans and the French mobilised their armed forces on August 1st. On the 2nd of August, the German government delivered an ultimatum to Belgium demanding the right of way through Belgian territory in order to enable an attack on France. The British Foreign Secretary, Sir Edward Grey, announced in Parliament that Britain would fight to defend Belgium should it be required. When the Belgians refused to agree to the German ultimatum and German troops entered Belgium anyway, the British responded by declaring war.Souce - gcsehistory.org.uk