The universal declaration of human rights was written in response to

the Holocaust

Explanation:

During the World War II, several genocides were taking place. The infamous Holocaust took place, where several ethnic groups were systemically murdered just because Hitler and his associates didn't thought they deserve to live. The most affected were the Jews, several Slavic people, and Gypsies. Millions of people lost their lives, and millions more barely managed to survive by the end of the war. All human rights were broken, and pretty much everything terrible that can be done was done. After the war was over, in order to stop such a thing to ever happen again, the universal declaration of human rights was written. While it has served in many occasions, unfortunately, the UN has also allowed similar things to happen on smaller scale, which is very weird considering the power this organization has.

after the french-indian war.