Executive Meddling: The whole "slave mine" aspect is not present in the original story. According to IMDB: "Author Barry Longyear reported at a convention that the studio insisted on adding a subplot involving a mine, thinking the audience would not realize that the "Mine" in the title was a possessive (as in "My Enemy") rather than an object." Fridge Logic kicks in when you realize a comma between Enemy and Mine would've solved the problem.
Troubled Production: The production began its shoot in Hungary with a different director and a $20 million budget (which was considered lower than the average sci-fi film). After the studio saw the first dailies, production was shut down and the director was let go. After Wolfgang Petersen was hired to replace the first director, the shoot moved to Germany with the budget somehow doubling to $40 million. Quaid and Gossett even got additional pay on their salaries so they would not abandon the production. Needless to say, Fox ended up with a major money loser by the time the film was released.
In Spanish the Enemy "Mine" confusion / Incredibly Lame Pun is non existent, being translated as Enemigo Mío ("Enemy of Mine") - not unlike Amigo mío ("My friend" / "Friend of mine") - so the true meaning of the title was kept, for once (we have a long tradition of They Changed The Title, Now It Sucks).