How did Hollywood cinema change in the years following WWII?

Question

How did Hollywood cinema change in the years following WWII?

Answer 1

After WWII Hollywood moved away from cheerful musicals that sustained the public through the Depression and rousing war stories that supported pro-war sentiment to serious and moody dramas often with moral ambivalence, called film noir. A key film of this genre was The Postman Always Rings Twice (1946). Many were based on literary works of the 1920s and 30s. This stylistic approach to filmmaking lasted through the 1950s.

http://en.wikipedia.org/wiki/Film_noir