Elias
Sargeant Elias is a bit more casual in his approach to downtime than Staff Sargeant Barnes who's straight-edged as Elias share a joint with his comrades. Ironically, Barnes isn't straight-edged about his military tactics as he literally commands his troops to rape and murder Vietnamese villagers. It's not until Elias shows up that anyone challenges Barnes.
Crossing the Line
Barnes interrogates a Vietnamese village chief and when he doesn't get the answers he wants he kills the chief's wife. The irony in this is that Barnes wants to take out those involved and by killing an older woman he's literally crossing the line between the battlefield and murder.
Elias' Death
Barnes tells Taylor that Elias was killed by the Vietnamese. Ironically, Taylor sees Elias, who's been shot, trying to escape the Vietnamese who eventually kill him. This makes it clear that Barnes has Elias' blood on his hands.
Smoking Dope
We watch as Taylor smokes a joint with Elias and his men. Ironically, by joining the more care free group in the platoon, Taylor is choosing a side that reflects moral character beyond that of Barnes and his hardened crew.
End of the War
Taylor is helicoptered out of the war zone in Vietnam. He says in a voiceover that the war is over for him now, but ironically it will live on with him forever. And we see the image of mass graves filled with the dead as he weeps, and we know that he will be haunted by his experience here forever.