In at least one hundred words, explain what purposes led Whitman to write "O Captain! My Captain!"

The poem is an elegy to the speaker's recently deceased Captain, at once celebrating the safe and successful return of their ship and mourning the loss of its great leader. In the first stanza, the speaker expresses his relief that the ship has reached its home port at last and describes hearing people cheering. Despite the celebrations on land and the successful voyage, the speaker reveals that his Captain's dead body is lying on the deck.