Bosnia
Assassination of Arch-Duke Ferdinand
Ferdinand, the heir to the Austrian throne, was assassinated along with his wife by a Sebian nationalist while touring Sarajevo.
Related: Entente Cordial | First Moroccan Crisis | Triple Entente | Sinking of Lusitania, Battle of Gallipoli | Battles of Verdun, Somme, Jutland | Wilson's 14 Points | Peace of Paris

Europe
The start of WWI
After aligning themselves into allied groups, the allied nations (Britain, France, Russia [to a certain extent], and all of their colonies) and the central powers (Germany, A-H and other antions within their spheres of influence) massed their forces and declared war on each other. The war is said to have started with the assassination of Arch-Duke Ferdinand.
Related: Entente Cordial | First Moroccan Crisis | Triple Entente | Sinking of Lusitania, Battle of Gallipoli | Battles of Verdun, Somme, Jutland | Wilson's 14 Points | Peace of Paris

France
The battle of the Marne
When the Germans attempted to invade France, they took a northern route through neutral Belgium. They met up with French and British troops at the Marne river, and a battle which pushed the Germans out was waged.
Related: Entente Cordial | First Moroccan Crisis | Triple Entente | Sinking of Lusitania, Battle of Gallipoli | Battles of Verdun, Somme, Jutland | Wilson's 14 Points | Peace of Paris

East Prussia
The battle of Tannenberg
This was a failed attempt by the Russia to occupy German land. They were pushed out by German troops.
Related: Entente Cordial | First Moroccan Crisis | Triple Entente | Sinking of Lusitania, Battle of Gallipoli | Battles of Verdun, Somme, Jutland | Wilson's 14 Points | Peace of Paris

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