Tim O'Brien's short short "Friends" is a companion story to "Enemies," which, ironically appears first (an inverted spoof on the phrase "friends and enemies"). Together, they function as complements to make one complete story which cannot be separated.
"Friends" is filled with irony: situational and verbal. Irony serves as a kind of morbid theme in the story, as Jensen and Strunk, once bitter enemies, become blood brothers. Together, they make a mercy-killing pact as a sadistic coping method for dealing with the cruelty of war.
Inevitably, Strunk is mortally wounded, and he fears that Jensen will enact the pact: "Jesus, man, don't kill me." Jensen must swear again not to kill. In the end, Jensen is relieved that Strunk dies from the injury, instead of facing his role as mercy killer : "Later we heard that Strunk died somewhere over Chu Lai, which seemed to relieve Dave Jensen of an enormous weight."
So, the themes and motifs in both stories revolve around their titles: In war, who is a "friend"? Who is a "enemy"? How can a soldier fight a two-front war? What extremes will men go to in dealing with fear: fighting, revenge, self-mutilation, mercy killing pacts? "Like fighting two different wars..."
In all stories, the theme of "carrying," or "weight," physical and emotional, is prevalent. Jensen carries a knife, a broken nose, a pact, guilt, fear, and--in the end--is relieved of guilt after Strunk's death. The war he fights is external and internal.
The tone of the story is both serious and comic, a kind of black comedy. As it is from the oral storytelling tradition, it is anecdotal and informal, as if O'Brien were telling the story "live"--like in a bar or a informal gathering. It is filled with realism (soldier-talk) and some fantasy (all the cruel ironies). As such, it is very post-modern--a self-conscious combination of many styles.
Technically, O'Brien tells the story in first person plural "we": "One morning in late July, while we were out on patrol..." The story is a flashback, as it is told twenty years later. As it is a war story, it's style tends to be more gruesome: In any other circumstance it might've ended there. But this was Vietnam, where guys carried guns, and Dave Jensen started to worry." So, O'Brien uses much bloody imagery ("Strunk's nose made a sharp snapping sound, like a firecracker...") and psychological commentary: "But that wasn't the bizarre part"--all of which lead to a story of gruesome reality and cosmic irony.
Like all the stories in the novel, a major theme is embedded in the story itself: storytelling. The telling of the story is as important as the content of the story: "the medium is the message." O'Brien's ability to play around with "truth," and "fiction" is what gives the story its greatest emotional weight.