In which year did the First World War begin?

1914 is correct because the July Crisis following the June 28 assassination of Archduke Franz Ferdinand set off a chain of alliance-driven war declarations. Austria-Hungary attacked Serbia; Russia mobilized; Germany backed Austria-Hungary and invaded Belgium and France; Britain entered after Belgium was violated—by August 1914, Europe was engulfed in war. Memory tip: “Fourteen for the First” (1914 = WWI; 1939 = WWII). 1917 marks turning points within WWI—the U.S. entry and the Russian Revolution—not its start, and 1930 falls between the wars amid the Great Depression. WWI introduced trench warfare, tanks, and chemical weapons and redrew borders, laying groundwork for later global conflicts.