There are many similarities between World Wars One and Two, one of the main similarities being surprise. No one expected the intensity of World War One and no one expected a war to erupt in the middles of the Great Depression. Before WWI, almost all the wars involved mainly two to three countries and were quick and decisive. What made WWI so strange was that it lasted from 1914 to 1918 and involved several countries worldwide, thus resulting in the name World War One. What made World War Two such a surprise is that almost no country wanted another war of such destruction, especially during the socioeconomic crisis that was the Great Depression. No one expected a leader such as Adolph Hitler to overtake an entire country and enact the world's greatest genocide. It certainly was a surprise that Japan would launch an attack on Pearl Harbor and at that time no one expected a nuclear bomb would end the war. Both wars had similar consequences. After the wars it left Germany in a bind, it left millions of people dead, and it still left tension among participating countries.
World War one originated through the Serbian assassination of Austrian Archduke Ferdinand in 1914. What made this war so unusual is the domino effect it had after the assassination. Because Russia wanted to protect its Serbs, they backed Serbia against Austria. Backing Austria was Germany, who was also opponents with France who had joined sides with Russia. Because of the Schlieffen Plan, Germany was forced to go through Belgium thus violating a neutrality treaty and bringing Britain into the war. Italy eventually backed Germany, and the U.S. joined late into the war against Germany. This ripple effect was caused by alliances, which also was why WWII was such a large war. World War One itself introduced some new technologies, such as faster firing guns and the introduction of trench warfare, but, just like in WW2, the war was lost when Germany tried to take over Russia.