When did the First World War start?  

1914 is correct answer.

Key Points

• The First World War began in August 1914. 
• It would span more than four years and kill almost nine million soldiers. 
• During the same time period, war and other violent conflicts were responsible for the deaths of an estimated twenty million civilians.
• Tensions rose after the assassination of Archduke Franz Ferdinand by Serbian nationalists on June 28, 1914. And at the time, the major European countries had an agreement that if one country declared war, the others had to intervene as well. 
• As a result, Austria-Hungary and Germany teamed up against the United Kingdom, France, Ireland, and Russia.

 Additional Information

• World War II was a terrible global struggle that lasted from 1939 to 1945. It entailed 100 million people from more than 30 countries. 
• World War II was the bloodiest conflict in human history, with 70 to 85 million people killed. 
• Tens of millions of people died as a result of genocides (including the Holocaust), famine, massacres, and disease. It remains the bloodiest conflict in human history to this day.
• The causes of World War II were numerous and varied, but it ultimately came down to Adolf Hitler and his Nazi Party's aggressive and expansionist goals.
• Furthermore, the severe Treaty of Versailles years before had simply created the groundwork for future confrontations.