Similarities and differences between the first and second world wars

The first and second world wars were very much alike, and at the same time unique. Each war was fought in different places, at different times. However, both wars were fought between many of the same countries, but for different reasons.
The beginning of WWI was surrounded by rising conflicts. Tensions caused by imperialism and strong nationalistic feelings caused countries to begin building up their militaries. Once the fear of war started, several alliances were made. Finally, the spark that set off the war was the assassination of archduke Franz Ferdinand of Austria-Hungary. This caused Austria-Hungary to invade Serbia, because Ferdinand was assassinated by a Serb. Then, all the treaties began to take effect, and everybody jumped in on one side or another.
The start of WWII had some similarities, but had a whole set of other reasons for taking place. First of all, after the first war, most of the world went into a depression. This ...