It was a global war originating in Europe that lasted from 28 July 1914 ti 11 November 1918. More than 70 million military personnel including 60 million Europeans , were mobilised in one of the largest wars in history. Over nine million combatants and seven milion civilians died as a result of the wars.
The trigger event was the assasination of Archduke Franz Ferdinand, It was not so significant event to star a World War, They started declaring the war just one week after the event, the countryes were already preparing the war before the event.
There were two important super-powers that wanted to control Europe(Great Britain and France) and (Germany and Austria-Hungary Empire)
Both super-powers were preparing the war with important military forces as they had colonies all over the world, but they also wanted to control all Europe(IMPERIALISM) So, the assasination of the Archduke of Austria-Hungary was the excuse triggerevent to start the war.
Trenches: Prepared by both sides of the war at the end of 1914 to defend themselves form the enemy. It was better tha open-air combat but anyway caused many victims and a stalemate due to the impossibility of both sides to go ahead in a secured way.
Zeppelin: Introduced in the war by Germany, it was used to drop bombs into England.
Bombs dropped by aeroplanes: More secured than zeppelins.
U-Boats: Invented by the Germans and very efficients to stop enemy naval warship but also to blockage againts enemy shipping.
Gas-attacks: Usecd in trenches to pison soldiers or make them gate out of them.
Armistice: Interruption of fight between opposing armies by agreement.
Allied powers: Apact of different powers fighting together. GB, France, Italy, Russia, USA, Japan, Serbia,etc...