The background of the poem Journey of the Magi by T. S. Eliot can be discussed on two levels, the first being the Biblical story from which Eliot derived his narrative and the second is the historical elements on which the Biblical references are based.
On the Biblical level, Eliot bases his story on the Nativity in the Gospel of Mark in which three wise men travel, guided by a star, to the manger' where the baby Jesus was born bearing gifts. The poem is set long after the event and the narrator looks back wondering the significance of what he had seen:
All this was a long time ago, I remember,
And I would do it again, but set down
This set down
This: were we lead all that way for
Birth or Death? There was a Birth, certainly, …
Historically, the "magi" were Zoroastrian priests who were expert in astrology and studied the movements and configurations of the stars to investigate the divine realm.
The opening five lines are taken almost word for word from a sermon preached on the Nativity of Christ before King Charles I by Lancelot Andrewes on Christmas day 1622.
The poem was written in 1927, the year in which Eliot became a British citizen and was baptized and confirmed having previously been a Unitarian. The Journey of the Magi reflects this momentous personal 'journey' in the life of the poet.