Every invention has societal consequences. Some are far-
reaching (polio vaccine) and some affect few, if any (the
golf tee). These inventions have indirect and direct
consequences.

Name the invention that was the major DIRECT contributor to
saving a way of life in the US and (less so) Britain.
Parenthetically, this invention was also INDIRECTLY
arguably responsible for the advancement of more human
misery than any other invention of the 19th century.

There may be more than one answer. I'm interested in what comes up.