Complex sentence: On his passage to Goa, he subdued the pirates at Mombassa who had been harassing the coast of Mozambique, which had been brought within the Portuguese trading orbit and provided watering stations essential to Portugal's lifeline to the west coast of India.
Split into simpler sentences: On his passage to Goa, he subdued the pirates at Mombassa who had been harassing the coast of Mozambique. Mozambique had been brought within the Portuguese trading orbit and provided watering stations essential to Portugal's lifeline to the west coast of India.