Austria-Hungary had invaded and crossed over into, Serbia and Russia was in an alliance with Serbia, so they felt as though they had to help out. Hope this helps.
It's important that we know where and how we came to be. For example we wouldn't really understand why you're a certain religion if we didn't know who settled the land and what happened. Not only that, but also a lot of things happened back then, a civil war, WWI and WWII, the Cold war, war of 1812, that made things what it is present day. Also history makes sure that we can honor people for freedom, such as Abe Lincoln who freed slaves. The point I'm making here is that history is a way to remember important events that have effected many things and many places and without keeping track of history (for example if we didn't keep track of the Constitution) we wouldn't have the somewhat peaceful society of today.
The reason why the presidential election of 1876 angered Democrats is because "Democrats thought the voting system was <span>unfair" since Tilden actually won the majority of the popular vote. </span>
