How did the assassination of francis ferdinard contribuet to world war 1?

Answer 1

It was a violent gesture of defiance of Austria-Hungary by Bosnian Serbs.

Germany urged the Austrians to take a tough line, promising to back them.

Russia mobilised its troops in support of the Serbs, though it was only a bluff - Russian being completely unprepared for war. But they refused to demobilise.

Germany was wrong-footed by this, because their only war-plan was based on invading France first and Russia second.

So after promising tough action, they felt they had no option but to start the war according to the only plan they had - which meant invading Belgium, thus bringing in the whole British Empire against them.