Conversation so far:
what's the historical background of the king in the musical the King and I
Mongkut, King of Siam, was about 57 years old in 1861. He had lived half his life as a Buddhist monk, and was an able scholar.
when did King Mongkut, King of Siam become king
After his twenty-seven years of monastic life, King Mongkut voluntarily defrocked and ascended the throne in 1851, aged 47.
how did nangklao, or Rama III, die
Nangklao died on 2 April 1851 without having named a successor.
what did the king of siam, Mongkut, do
Mongkut, also known as King Rama IV, ultimately succeeded in keeping Siam an independent nation, partly by familiarizing his heirs and harem with Western ways.

Question: what is his major accomplishment
Self-contained rewrite: what is King Mongkut's major accomplishment