The Man Who Would Be King

Ruchira Paul in Accidental Blogger:

The Man Who Would Be King is the improbable life story of American Josiah Harlan, a young Quaker from Chester County, Pennsylvania. In 1822, Harlan, an earnest young man of twenty two, robust in health and florid in his imagination, set out to seek a new life with nothing more at his disposal than a love of adventure, history (especially the exploits of Alexander the Great of Macedonia) and botany.  His journey began in Philadelphia and landed him in Calcutta, India, by way of China in 1824. In India he enlisted as an assistant surgeon in the army of the East India Company (the precursor to the British Raj) although the only medical knowledge Harlan possessed came from a medical manual he read during his ocean crossing. After being injured during battle in Burma, Harlan obtained his discharge from the Company's army and traveled to northwest India and Afghanistan, seeking to realize his fondest dream - to follow in the footsteps of Alexander the Great.

For several  years, Harlan crossed and re-crossed the border between India (now Pakistan) and Afghanistan. In a political climate, where every man was spinning in a private orbit of political ambition, alliances were made and broken with dizzying pace.  Harlan played the field on several different sides with the keen eye of a mercenary. He accumulated considerable wealth, acted as a doctor and a governor to a powerful Indian king, sided with and opposed the British and conspired for and against several Afghan aspirants to the throne.

More here.