Complex sentence: On May 20,1778, a British attempt at encircling a smaller Continental force under the Marquis de Lafayette failed, the Continentals escaping, but the British took the field.
Split into simpler sentences: On May 20,1778, a British force attempted to encircle a smaller Continental force under the Marquis de Lafayette. The maneuver failed, with the Continentals escaping the trap, but the British took the field.