Dulce et decorum est pro patria mori is a line from an ode by the Roman lyrical poet Horace. [Odes (III.2.13)]
The line can be roughly translated into English as: “It is sweet and fitting to die for one’s country.”
POEM SOURCE: Cecil Day-Lewis, and Edmund Charles Blunden. Editors. The Collected Poems of Wilfred Owen. New York: New Directions, 1963. Print.