Wilfred Owen's classic poem "Dulce Et Decorum Est" was written in the latter part of 1917 and the first few months of 1918. The title of the poem comes from a Latin poem that Horace wrote about 1900 years earlier.
Owen concludes poem by adding the full phrase from Horace, who adds the words "pro patria mori." Thus, the entire phrase may be translated, "Sweet and fitting it is to die for one's country."
A glance, however, at the preceeding lines of Owen's poem make it clear that death during World War I was anything but pleasant. The soldiers are covered in blood; they can barely walk; they can barely see; they are drowning under the sea of poisonous gas.
A soldier suffering from the gas has "white eyes writhing in his face" and his face is "hanging...like a devil's sick of sin." The "c", "g", and "f" sounds in the following line almost do allow Owen's audience to hear a soldier choking to death because of the gas: "Come gargling from the froth-corrupted lungs."
Such a death is so horrific that Owen tells his audience that Horace's phrase, in view of such a terrible death, has no truth to it:
My friend, you would not tell with such high zest
To children ardent for some desperate glory,
The old Lie; Dulce et Decorum est
Pro patria mori.