If you haven't buffed up on Latin lately, don't worry. Your friendly Shmoop translation team is here to help.
These Latin lines are quoted from Horace (a Roman philosopher and poet).
Here's the lines in English: "It is sweet and proper to die for one's country."
After reading all of the stuff that our speaker (and our speaker's comrade) have gone through, it's pretty hard to believe that Horace actually knows what he's talking about.
We're guessing that that's Owen's point.
Notice how the last line of the poem doesn't have anywhere close to ten syllables?
For readers accustomed to seeing or hearing a line that's ten syllables long, this would sound like a huge, awkward silence.
Maybe like the silence of death.