Germany was very annoyed with what Russia was doing, so in response, they tried to declare war on Russia to let Austria go to war with Serbia.

2 days later, Serbia accepted all but 1 or 2 of Austria’s demands, those few being minor clauses.

Germany was planning to invade France, but they needed to get there. So, they just decided to invade Belgium first. The result was a German victory.

Ferdinand is assassinated by the Black Hand because of his perceived threat to Serbian independence.

Germany declares war on France because of France backing up Russia.

Austria felt that it had no choice but to assert its dominance against Serbia, despite the ultimatum. They wanted to squash support for Serbian nationalism.

Great Britain tried to stay neutral in the European conflict, but the invasion of Belgium tipped them into favor against Germany. So, they declared war against them.

Despite not being allies with Serbia, Russia wanted to deter Austria from invading them by playing troops near their border.

After the assassination of Archduke Ferdinand, Austria issued Serbia with an ultimatum to prevent an escalation or war.

Austria had Germany’s support, so when Russia mobilized near Austria, Germany stepped in, telling Russia to stop mobilizing and for France to stay neutral. France did not listen.