What was a result of the use of chemical weapons during World War I?

The widespread use of poison gas during World War I led many nations to seek restrictions on chemical weapons. The 1925 Geneva Protocol prohibited the use of chemical and biological weapons in war, making “Many nations agreed to stop using chemical weapons after World War I” the best answer. Tanks and aircraft were not developed specifically to counter poison gas, and trenches did not reliably protect soldiers from it.

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