I choose World War II.
It was not just about armies fighting each other but also concerned the
decimation of an entire race of people.
During WWII, the Germans tried to
wipe out the Jews in Europe and almost succeeded had not the allies arrived and
liberated the camps where the Jews were held. This also led the establishment of international laws to prevent genocide and convict those who perpetuate it.
Spanish became a primary language for many Latin American countries.
The answer would be the leather product industry. During the period of 1879 to 1909, there was a rise in less expensive products overall. So it happened to the iron and steel industry which rose because it had just become cheaper to manufacture at high quantities; but what increased its presence in the economic field, was the cotton industry, that was rising quickly, which made the leather products, that were more costly and time-consuming to manufacture to fall three rankings from 1879 to 1909.
One advancement was the creation of the alphabet (Which most of the current alphabets are based on.)
