Complex sentence: Sartorius spent a great deal of his own money in keeping the fleet together, but when he threatened to sail off with it until he was paid, Dom Pedro sent two English officers to the flagship; one to arrest Sartorius, the other to take command.
Split into simpler sentences: Sartorius spent a great deal of his own money in keeping the fleet together. When he threatened to sail off with it until he was paid, Dom Pedro sent two English officers to the flagship; one to arrest Sartorius, the other to take command.