The immediate cause of World War I that made the aforementioned items come into play (alliances, imperialism, militarism, nationalism) was the assassination of Archduke Franz Ferdinand of Austria-Hungary. In June 1914, a Serbian-nationalist terrorist group called the Black Hand sent groups to assassinate the Archduke.
Weimar Constitution adopted in Germany
A) The South didn't need to conquer the North to win its independence.
The South was just planning on defending itself till the North grew tired, but the North had to conquer the South to be able to reunite the Union and win the war.
Secondary sources is the right one
Well a number of things but most likely, the resources would go down but probably not by much. I hope this as helped :D