## TL;DR

World War I (1914-1918) was the first industrial-scale global conflict. Trigger: assassination of Archduke Franz Ferdinand (June 28, 1914). Alliances: Central Powers (Germany, Austria-Hungary, Ottoman Empire) vs. Allies (France, UK, Russia, Italy, US from 1917). Trench warfare, machine guns, poison gas, tanks — ~20 million deaths.

## Core Explanation

Schlieffen Plan: Germany's two-front strategy failed at First Battle of Marne (1914). Western Front: stalemated trench warfare from Switzerland to English Channel. Verdun (1916): 10-month battle, 700,000+ casualties. Somme (1916): 1 million+ casualties. US entry (1917): tipped balance. Armistice (Nov 11, 1918). Treaty of Versailles (1919): harsh terms on Germany → resentment → WWII seeds.

## Further Reading

- [The Guns of August (Barbara Tuchman)](https://www.penguinrandomhouse.com/books/56337/the-guns-of-august-by-barbara-w-tuchman/)