This question already has an answer here:
Would it make sense for a society to maintain a strong military in the absence of a major adversary, given certain aspects of its history? I am writing about a future in which humanity has a very militaristic structure with a strong military presence, but (until the primary events of the story) there is no comparable force that could oppose them. There are pirate leagues and independent colonies, but they are not quite a significant threat to warrant heavy militarization.
Previous to society's current state Earth was made uninhabitable by a catastrophe that ended the fourth world war. Most of humanity united out of a need to survive in scattered colonies around the solar system. The fact that all factions were in a military stance at the time and military rationing allowed for improved survival make sense for starting as a militaristic society.
That said, the story is suppose to take place about 200 years later when humanity has advanced into a limited interstellar capacity. It has recently been outed that the government became aware of an alien race similarly, but slightly less, advanced than us who as of yet seems to be unaware of us. Obviously the discovery of the aliens would warrant militarization, but would the militarization have survived enough through 2 centuries of peace for nobody to think anything different?
I am just not sure if there are any real history examples that could support it or would I lose the reader right away with the simple question of why is the military still so important.
EDIT: There is another question that is similar to mine, however it differs in that my society has no known counterparts. No other nations that could possibly rise up. Most of that questions answers seemed to revolve around preparation for known possible threats from other known societies. Mine is a society where, until the events of the story, they had no credible threats.
That said I think I have gotten sufficient answers to my question. Thanks all!