Why was World War I initially described as 'the war to end all wars,' and why did that expectation prove false?

• A. It was framed as a war to resolve conflicts; but unresolved grievances and new imperial ambitions led to WWII.
• B. It was expected to be brief due to rapid mobilization and industrial capacity.
• C. It resolved all major conflicts and prevented future wars forever.
• D. It created a lasting peace foundation that prevented any future wars.

Answer: (A)

The idea being tested is why people hoped World War I would usher in lasting peace and why that hope didn’t last. After the war, leaders believed the conflict could be settled in a way that would remove the causes of future wars. This optimism fed the push for a new international order—equality among nations, collective security, and new rules for diplomacy (the League of Nations and treaty commitments). Because of that belief, the war came to be described as the war that would end all wars.

But the peace that followed didn’t eliminate the underlying tensions. The treaty settlements left many grievances unresolved, especially German resentment over reparations, territorial losses, and the sense of humiliation. At the same time, old and new imperial ambitions kept rivalries alive—and nationalism, economic troubles, and political upheaval spread across Europe and other regions. When these tensions reemerged in the 1920s and 1930s, they contributed to the rise of aggressive regimes and new conflicts, culminating in another large-scale war. So the phrase captured an era’s hopeful belief in a durable, international mechanism to prevent future wars, but the unresolved grievances and renewed ambitions proved too powerful to prevent another global conflict.