What were the main causes of world war i?

Why is the date 1607 important? Who was Columbia named after? What country was Charlemagne born in and work in? What was the Columbian exchange and what impact did it have on Europe and The Americas? What explorer was credited as the first to circumnavigate the world? Which event in 1453 had significant impact on the European world? What was the Potsdam conference in 1945? When did Juan peron go into exile? Who controlled the region in southwest Asia after World War 1? How many years have passed since the Hopi village of Oraibi was founded? Who is the most important person in medical history? What did William of orange do? Who created an excuse to attack Austria? Qianlong did not what? How did the iron plow help other countries? In World War 1 what was the name of the treaty that ended World War 1 and what did it do? Does Songhai still exist? How was the people treated during world war 2? How does maria theresa and Philip II RELATE? What fictional character did early Americans have something in common with?