Complex sentence: In 1784 Johann Friedrich joined the army, fighting in the French Revolutionary Wars from 1793 to 1795 before joining the diplomatic service in 1803 on Napoleon's occupation of Hanover and leaving for the United Kingdom.
Split into simpler sentences: In 1784 Johann Friedrich joined the army, fighting in the French Revolutionary Wars from 1793 to 1795. In 1803 he joined the diplomatic service on Napoleon's occupation of Hanover and left for the United Kingdom.