Question

why do you think in the poem small pain in my chest the poet has disguised himself as a narrator

Answer 1

May be the poet wants to tell the difficulties faced by a soldier,when he goes for the fight or war.
In this poem,the soldier have a small pain in his chest and we can see that in most of the paragraph 'A Small Pain In My Chest' is repeated.At last the soldier dies on the lap of the poet.