The cynical main character eventually learns to give up on his beliefs and training in order to open himself up to another person. Also, audiences can learn a little about "numbers stations" and the way they broadcasted coded transmissions during WWII (and, apparently still do).
Both of the main characters are serving their country, but they either perform deeds that they don't understand (like sending secret codes), or distasteful and illegal ones (like murder). Ultimately, they decide that their humanity is more important than their job.
The main character is a trained killer, and he shoots and kills several men over the course of the film. Bad guys shoot back at him and blow up a car. In a fantasy sequence, the main character envisions killing the heroine of the movie. In real life, he fixes her wounds, pulls a hunk of shrapnel from her leg, and stitches her leg up. Blood is shown. There's a huge explosion at the climax.
Some minor romantic tension between the two main characters; by the end, it appears that they're going to be a couple, but there's no kissing, innuendo, or sex of any kind. In an early scene, a man touches a woman's back, indicating that they're a couple.
Language is fairly infrequent but includes about a dozen uses of "f--k" and a couple of uses of "s--t." "Bastard," "ass," "Jesus Christ" (as an exclamation) and "oh my God" are also used.
Drinking, Drugs & Smoking
The main character claims that he "was a drunk" but that he gave up drinking. Nonetheless, he's seen drinking alone in a hotel room early in the film. A minor character also claims that he hasn't had a drink in three years but drinks a shot of scotch.