The submarine.
Because the whole world was basically in the war
The 30.cal machine gun.
The Serbian assassination of the Austrian Archduke Ferdinand.
It turned the tide of war in Allied favour
The assassination of the duke, Franz Ferdinand started it. It turned into a world war because everyone was pointing fingers at each other
Chemical weapons (warfare)
WW II became a global war because it was started by nations that had global ambitions; if you try to take over the whole world, you will have a global war.
WW1 was the war to end all wars. Prior to WW2, WW1 was called, "The Great War."
There can be no doubt that the most deadliest weapon of world war 2 was the nuclear bombs that dropped on Hiroshima.
The most common one that was used as a weapon in World War 1 is called the Artillery
Man.
guns
None
The most common method was with artillery.It is NOT a biological weapon, it is a chemical weapon.
broken pistolthe zeppelin was the least important weapon in ww1.
the tank
Propaganda.