There were two primary alliances that were established prior to world war i. what were they called?

Why is it useful for historians to base certain studies on the analysis of historical periods

In italy, the distance between milan in the north and palermo,sicily, in the south is about 550 miles. in the united states, the distance betweenboston, massachusetts, and savannah, georgia, is about 900 miles. do you think the american revolutionaries of 1776 in the 13 colonies faced some of the same challenges as the patriots who struggled for italian unity in the 1860s?  

What are some effects outside of europe because of world war 1?