Complex sentence: Rodney was appointed United States Minister to the Argentine Republic in 1823--he had spent a number of years in foreign service before this appointment, serving on a 1817 commission of President James Monroe to investigate whether newly formed South American republics should be recognized.
Split into simpler sentences: Rodney was appointed United States Minister to the Argentine Republic in 1823. He had spent a number of years in foreign service before this appointment, serving on a 1817 commission of President James Monroe to investigate whether newly formed South American republics should be recognized.