The entry of the US with fresh troops when the troops of both original sides were already exhausted.
U-boats.
the machine guns
landcaster
When Italy switches sides and The Russian Revolution
Japan
In France they planted a tree when world war 1 was ended and the tree fell at world war 2 so what changed no more tree
Alot has changed the world like World War 1 because it had so much to do with civics today
it changed peoples opinions on how the next war would turn out to be
Poland, Germany
it changed it and all the stuff around it :)
cause it flys
gajkl