Complex sentence: With the British paying higher prices, they were significantly undermining Dutch aims for a monopoly, and as Dutch-British tensions increased, the Dutch built, in 1611, the larger and more strategic Fort Belgica, above Fort Nassau.
Split into simpler sentences: With the British paying higher prices, they were significantly undermining Dutch aims for a monopoly. As Dutch-British tensions increased, the Dutch built, in 1611, the larger and more strategic Fort Belgica, located above Fort Nassau.