World War I or "The Great War" as it was called, was one of the bloodiest conflicts in human history. Caused by centuries old rivalries and vicious quests for power, it brought many great nations to war.
The costs of WWI were high; 8.5 million soldiers killed, over 30 million total casualties, and $185 Billion in money spent. (1914 dollars)
Amazingly enough WWI did not solve many problems. European nations went into economic decline, radical dictators came to power, and the seeds of despise were planted on the European continet. These seeds would sprout a 2nd world war that was to be deadlier than the first.