The movie M*A*S*H was released in 1970, and after 46 years (and the lengthy run of the subsequent television series), it's a cultural earthquake we all tend to take for granted. But is is seismic nonetheless.
From Roger Ebert's original review:
We laugh, not because "MASH" is Sgt. Bilko for adults, but because it is so true to the unadmitted sadist in all of us. There is perhaps nothing so exquisite as achieving (as the country song has it) sweet mental revenge against someone we hate with particular dedication. And it is the flat-out, poker-faced hatred in "MASH" that makes it work. Most comedies want us to laugh at things that aren't really funny; in this one we laugh precisely because they're not funny. We laugh, that we may not cry.
We watched it again last night, and if you have not seen this movie in a while, consider returning to it.