It would be the north american Free trade agreement
1.) John Locke sided with the protestant parliament against the Roman Catholic King James the second in the Glorious Revolution of 1688-1689.
2.) In 1960, Locke published his book Treatises Of Government where he argued natural rights of the human being such as life and liberty.
3.) Locke's writing influenced many famous writers such as Voltaire and Rousseau.
4.) A little less than 100 years after Locke published his treatises of government, Thomas Jefferson used his theory in the declaration of independence!
5.) Locke believed that the natural rights of individuals limited the rights of the king.
The correct answer is the Influenza Pandemic.
This Influenza (flu) Pandemic killed between 20 and 100 million people (estimates differ) - more than the war itself!
The source of the Pandemic is still not known, and people suggest such places as the US, China and France.