| I don't really know that much about the Seven Years war, but I think that the reason why it's not counted as the First World War is the communication capabilities at that time.
It was very hard for the military leaders to keep track of all that was happening, so it was more like many small wars around the world, rather than one large one.
The Roman's conquests around the (known) world at that time could also be counted as a world war because of all the "countries" involved, but it isn't. |