What are the themes of Thackeray's "King Canute?"

W.M.Thackeray's (1811-1863) poem "King Canute" drives home the moral that all men no matter how great they are will have to die some day or the other and that no matter how great a person  is or how much he has achieved, all his greatness and achievements are nothing compared to the awesome power of God the Creator and Controller of the Universe and all that is in it.

A subsidiary theme would be Thackeray's caustic satirical attack on the universal vice of sycophancy. At all times in all parts of the world sycophancy is and will continue to be a prevalent vice: "King Canute is dead and gone: parasites exist alway."

Thackeray narrates the legend of King Canute who after a long and hectic reign characterized by much violence:

"Cities burning, convents blazing, red with sacrilegious fires;
Mothers weeping, virgins screaming vainly for their slaughtered sires.—"

was bemoaning his weakness and his age as he was walking along the shore one day with his retinue of fawning courtiers. He confesses that he is "sick and tired and weary" and wishes for an early and peaceful death: "Would I were [dead] and quiet buried, underneath the silent mould!"

Immediately his sycophantic courtiers try to cheer him up by saying that he will live for another fifty years at least or like the Biblical characters even for a thousand years! The Bishop flatters him by remarking, "Death was not for him intended." The King decides to teach his courtiers a lesson. He asks the Bishop whether the waves of the sea will obey him, immediately the Bishop replies that they will:

"Will the advancing waves obey me, Bishop, if I make the sign?"
Said the Bishop, bowing lowly, "Land and sea, my lord, are thine."

But when he orders the waves to obey him the waves refuse to do so and rush into the shore carrying with them the king and his courtiers. The courtiers learnt a lesson that day which they never forgot for the rest of their lives. From that day on King Canute never wore his golden crown and ordered his courtiers never to kneel in front of him:

"And he sternly bade them never more to kneel to human clay,
But alone to praise and worship That which earth and seas obey:
And his golden crown of empire never wore he from that day."