Complex sentence: The force he engaged was the fleet carrying the troops of Rochambeau to North America, and was too strong for his squadron of two small ships of the line, two fifty-gun ships and a frigate.
Split into simpler sentences: The force he engaged was the fleet carrying the troops of Rochambeau to North America. It was too strong for his squadron of two small ships of the line, two 50-gun ships, and a frigate.