Complex sentence: On September 15, General Howe attacked the Continental Army force stationed at New York City, then located only on lower Manhattan, and landing at Kip's Bay, drove the Americans out of the city and captured all of the cannons they had there.
Split into simpler sentences: On September 15, General Howe attacked the Continental Army force stationed at New York City, then located only on lower Manhattan. They landed at Kip's Bay and drove the Americans out of the city, capturing all of the cannon that they had there.