Welp now Europe is divided into different chunks. There's Austria-Hungary and the Ottoman Empire, Russia is still Russia, Great Britain is still Great Britain, France is still France, and Germany is still Germany. (hmmm everything is still everything)
Here's the big picture. Some Bosnian-Serbians, living in Austria-Hungary, were really mad because THEY DIDN'T WANT TO BE PART OF AUSTRIA-HUNGARY. (man if you could control things like this just go with the flow stoopid) So, they try to kill the heir to the king. The "Black Hand", a secret society by Danilo Ilić, tries to kill the Archduke Franz Ferdinand. On the 28th of June, 1914, our good friend Franz visited the Bosnian capital Sarajevo. Mr. Ilić, being the good Serbian as he is, stations a "few" assassins along the route which the motorcade would travel.
As the Archduke travelled along the Miljacka River, the first assassin lost his nerve and did absolutely nothing. The second one, next to the first assassin, also failed to act. What a bunch of wimps. The third, Čabrinović, had a bit more determination and threw his grenade. And guess what? HE FAILED. (bruhhhhh) It hit the car behind the Archduke and Mr. Ferdinand escaped unharmed. After this failure, Čabrinović got arrested and the rest of the assassins trudged away, and the Archduke went to the city hall for a scheduled reception. Apparently, the attack stressed him out, interrupting the mayor's speech. After calming down, he decided to go check on the people injured by the grenade thrown by Čabrinović. Simple, right? Well, it wasn't. The general wanted to avoid the crowded city center. So, he made a new route that would travel straight along the Appel Quay to the Sarajevo Hospital. Except, they forgot to tell the driver. Which proved to be a VERY fatal mistake. The soon-to-be assassin, Gavrilo Princip, was waiting for them. After the initial failed attempt on the Archduke's life, he thought: Well, wouldn't it be great to catch him on the way back? And so he did. Stopping nearby a shop, he saw the first and second cars turn suddenly and leave the Appel Quay. As the third car followed, the governor, along with the Archduke and his wife told the driver that he was going the wrong way. As the driver braked, Princip walked up to the car and shot the Archduke and his wife at point blank range.
Understandably, Austria-Hungary is angered about all of this. And so begins the July Crisis, diplomatic manoeuvring between different countries. Its really complicated, but to make things short, Austria-Hungary really wanted to start a war. And so they did. First, they sent an ultimatum of impossible demands to Serbia. Here's the list:
Suppress all publications which "incite hatred and contempt of the Austro-Hungarian Monarchy" and are "directed against its territorial integrity".
Dissolve the Serbian nationalist organisation ("The People's Defense") and all other such societies in Serbia.
Eliminate without delay from schoolbooks and public documents all "propaganda against Austria-Hungary".
Remove from the Serbian military and civil administration all officers and functionaries whose names the Austro-Hungarian Government will provide.
Accept in Serbia "representatives of the Austro-Hungarian Government" for the "suppression of subversive movements".
Bring to trial all accessories to the Archduke's assassination and allow "Austro-Hungarian delegates" (law enforcement officers) to take part in the investigations.
Arrest Major and civil servant who were named as participants in the assassination plot.
Cease the cooperation of the Serbian authorities in the "traffic in arms and explosives across the frontier"; dismiss and punish the officials of and frontier service, "guilty of having assisted the perpetrators of the Sarajevo crime".
Provide "explanations" to the Austro-Hungarian Government regarding "Serbian officials" who have expressed themselves in interviews "in terms of hostility to the Austro-Hungarian Government".
Notify the Austro-Hungarian Government "without delay" of the execution of the measures comprised in the ultimatum.
And Serbia, not really wanting to start a war, decides to just refuse one of them, being Number 6. Austria-Hungary, who REALLY wants to go to war over this, uses "Serbia refused one of my demands!" as an excuse and declared war on Serbia.
Germany, being Austria-Hungary's ally, also declares war on Serbia. Russia, which is Serbia's ally, declares war on both Germany and Austria-Hungary. France, being Russia's ally, declares war on Austria-Hungary and Germany. Caught up yet? In case you didn't, well, then TOO BAD