On June 28, 1914, an assassin murdered Archduke Franz Ferdinand of Austria and his wife Sophie, the duchess of Hohenberg. The murder took place Sarajevo at the hands of a Serbian radical.
On July 28, 1914, Austrian Emperor Franz Joseph, declared war on Serbia.
On July 31, 1914, Russia, an ally of Serbia, mobilizes troops and goes to Serbia’s defense.
On August 1, 1914, Germany, an ally of Austria, mobilizes troops and declares war on Russia.
On August 3, 1914, Germany declares war on France.
On August 4, 1914, Germany declares war on Belgium and launches a quick strike through the neutral nation in hopes of attacking France from the north. Great Britain declares war on Germany in response to their invasion of Belgium.
On August 6, 1914, Austria declares war on Russia and most of Europe is engulfed in war.
In the earliest days of aerial warfare, planes played a rather minor role as many military leaders worldwide did not believe in their usefulness. Then some pilots began dropping small handheld bombs over enemy targets. Then some pilots tried using machine guns to shoot at their targets and other planes, but they could not shoot straight ahead without hitting their own propellers.
On this day, June 24, 1915, Germany rolls out their revolutionary new fighter plane, the Fokker Eindecker also known as the Fokker E. Eindecker translates as monoplane. What made the Fokker E so revolutionary was that it had a machine gun mounted straight ahead that was synchronized to fire with the engine so that the bullets would not strike the propellers. When the Fokker E took to the skies, it was the deadliest plane of the early days of the war. Not long after, the Germans managed to mount two forward facing synchronized machine guns, doubling the deadly effectiveness of the plane. The Germans were so protective of the synchronizing technology that the Fokker E was only allowed to fly over Germany for fear that one would be shot down elsewhere and the technology discovered.
On August 1, 1915, German pilot Max Immelmann, the infamous German Ace, recorded the first Fokker E kill. By the end of World War I, the Fokker E was credited with over 1,000 kills of Allied aircraft.
It wasn’t until 1916 that Great Britain sent their own version of a Fokker E into the skies, equipped with a synchronized machine gun somewhat equalizing aerial warfare.
Sources for the above includes: World War I Timeline; First Operational Flight of New German Fighter Plane; Quest for Performance: The Evolution of Modern Aircraft; The 6 Most Lethal Aircraft in History; German Aviation: Fighters 1915; Fokker E (Eindecker) Armed Monoplane Fighter / Scout (1915).