Which set of lines in this excerpt from W. B. Yeats's "An Irish Airman Foresees His Death" suggests that the speaker voluntarily chose to take part in the war?
I know that I shall meet my fate
Somewhere among the clouds above;
Those that I fight I do not hate,
Those that I guard I do not love;
My country is Kiltartan Cross,
My countrymen Kiltartan's poor,
No likely end could bring them loss
Or leave them happier than before.
Nor law, nor duty bade me fight,
Nor public men, nor cheering crowds,